Regret (Level)

Regret is a Halo 2 campaign level. Starting from the end of the previous level Delta Halo, travel on floating gondolas, in underwater elevators, and through various temple corridors to reach the room holding the Prophet of Regret.

Usable Weapons

 * Battle Rifle
 * Beam Rifle
 * Carbine
 * Energy Sword
 * Fuel Rod Cannon
 * Magnum
 * Needler
 * Plasma Pistol
 * Plasma Rifle
 * Rocket Launcher
 * Shielded Plasma Cannon
 * Shotgun
 * SMG
 * Sniper Rifle
 * Assassins Skull

Vehicles Encountered

 * Banshee
 * Phantom (non-drivable)
 * Pelican (non-drivable)

Testament
{Cutscene}

Master Chief starts to walk past a hologram of Prophet of Regret chanting a sermon

Cortana: "Wait, go back."

Master Chief puts Cortana in the holo-projector, her avatar appears

Cortana: "That's what I thought he said. The Prophet of Regret is planning to activate Halo!"

Master Chief: "Are you sure?"

Cortana snaps her fingers, the hologram starts speaking in English

Prophet of Regret (Hologram): "I shall light this holy ring, release its cleansing flame, and burn a path into the divine beyond!"

Cortana snaps her fingers again, and the hologram freezes.

Cortana: (smugly) "Pretty much."

Master Chief: "Commander, we've got a problem."

Commander Keyes (O.S.): "So I hear."

The view changes into In Amber Clad's bridge, where Keyes studies a hologram of the Index.

Commander Keyes: "But from what I understand, the Prophet will need an object, the Index, to activate the ring."

Commander Keyes changes the hologram to the Library

Commander Keyes: "I've located a Library similar to the one you found on the first Halo. If the rings work the same way, the Index should be inside."

Sergeant Johnson (O.S.): "I'll bet the Covenant are thinkin' the exact same thing."

Commander Keyes: "Then, we'd better beat them to it, Sergeant. Extract your men, and meet me at the Library."

Sergeant Johnson (O.S.): "Yes, ma'am."

The view changes back to Master Chief and Cortana.

Commander Keyes (O.S.): "I'll secure the Index, Chief."

Master Chief puts Cortana back in his armor.

Commander Keyes (O.S.): "You take out the Prophet. He's given us all the intel we need."

{Gameplay}

Cortana: "You know, I think the Forerunners built these new structures around the old, to protect them, to honor them. Pure speculation, mind you. I'd need to make a thorough survey to be sure."

Once the Chief and his Marine companions clear the nearby areas and reach a platform where a Gondola will stop.

Commander Keyes: "Cortana, the Covenant are getting nosy. I don't want to give away my position, so I'm rerouting a few stragglers back to you. I apologize; these Pelicans are all the support you're going to get."

Cortana: "Understood, ma'am."

Cortana: "A gondola's launching from the far towers. Big surprise, it's full of Covenant reinforcements.

After all hostiles are eliminated by the Chief.

Cortana: "Well, they were nice enough to bring us a ride."

If either Private Chips Dubbo and/or Sergeant Stacker are with the Chief.

Pvt. Chips Dubbo:"Alright, everyone aboard."

GySgt. Stacker:"I'll drive."

Pvt. Chips Dubbo:"Whats to drive?, It comes here, It goes there."

If the Chief waits around the Gondola.

Cortana: "This gondola won't get us all the way to the main temple, but it'll get us close. Let's get on board."

If the Chief continues to wait.

Cortana: "If you hit the activation switch, it should drive itself."

One-Way Ticket
{The Chief and the two Marines are attacked by a swarm of drones as they cross the lake.}

{After the last drone is killed.}

Cortana: "This lake couldn't have been created by volcanic action, which means it was either built this way on purpose, or was created by some other cataclysmic event. Sorry, were you trying to kill something?

When the Chief and the Marines clear the Gondola—stopping area of Covenant and reach the first underwater elevator.

Cortana: "Ah, now I see. There's a submerged section that connects these towers to the outlying structures. Looks like we're going down. Unless you'd prefer to swim."

Pvt. Chips Dubbo: "Full car, comin' up!"

If the Chief waits around for too long.

Cortana: "All right, let's see where this elevator goes."

As the Chief and the Marines journey underwater in the elevator, and peer around the murky depths, a fimiliar theme plays.

Cortana: "I've intercepted a secure transmission from Regret's Carrier to the something called High Charity. It seems to be a formal apology to the Prophets of Truth and Mercy. Apparently, Regret jumped the gun when he attacked Earth. He's asking the other Prophets to 'forgive his premature arrival,' arguing that 'no human presence was foretold.' That explains why there were so few ships in his fleet. But it's odd that a Prophet would have such bad intel about his enemy's homeworld."

Once the Chief and the Marines that are alive clear the current area of Covenant, in a large chamber, looking at the huge hologram of the Prophet of Regret.

Cortana: "And people say I've got a big head."

If you stare at Regret's hologram for long enough.

Prophet of Regret (Hologram): "Most of those we encountered in our search were compelled to join our Union. To take part in moment of promise, Freedom for allegiance, Salvation for service! But some, like the Humans, chose to impede our progress. Block our access to Sacred sites, damage Holy Relics! For their transgressions, the Humans shall be hunted until none remain alive!"

Pvt. Chips Dubbo: "Oh man, he's so dead."

If you wait around long enough.

Cortana: "Keep moving. Let's find our way back to the surface."

When the Chief and surviving Marines reach another submerged elevator and go underwater again.

Cortana: "Regret's carrier just received a response from High Charity. A very well encrypted message from the Prophet of Truth. Listen to this: 'Your haste has jeopardized the fulfillment of our Covenant and threatened our grand design. That you shall be spared a public display of our contempt is thanks only to Mercy and his wise counsel'. Truth, Mercy, Regret. Three Prophet hierarchs. Killing Regret should shake up the Covenant leadership. But frankly, it sounds like you might be doing Truth a favor."

After emerging from the elevator, there is another hologram of the Prophet of Regret spouting religious rhetoric and chanting.

Prophet of Regret (hologram): "Every member of the Covenant shall the walk the path. None will be left behind when our Great Journey begins! That is the Prophets' age-old promise. And it shall be fulfilled!"

Cortana: "'Great Journey'? Doesn't he know what these rings do?"

Later, when the Chief clears the nearby outdoor area of Covenant and secure a landing zone.

Pelican Pilot: "This is my last run, Chief! I'm nearly out of fuel. We've secured the first tower cluster, so I'll set down there. Call when you're ready for evac."

The Pelican drops off more weapon pods and some Marines.

The Chief and the Marines clear the next nearby outdoor structure area of Covenant, and encounter another gondola. (Only 2 Marines will follow you.)

Cortana: "There, another gondola. Looks like it leads straight to the main temple. Not much further now."

Pvt. Chips Dubbo: "Oh great! We're gonna ride another one of these death-traps!"

Marine: "If you forget about the Covenant and the fact we're stuck on some freaky alien world, it's actually kinda fun."

As the Chief starts the gondola.

Commander Keyes (O.S.): "How's it going, you two?"

Cortana: "So far, so good. We're approaching the main temple now."

Commander Keyes (O.S.): "Roger that. I'm as close to the library as I can get. There's some sort of ... barrier. We're trying to find a way around it. I'll keep you posted."

Sorry, Were You in the Middle of Something?
{Cutscene}

''The Master Chief walks off the gondola and looks around, then up. There are an uncountable number of Slipspace ruptures, and hundreds of Covenant ships come out of Slipspace.''

Cortana: "That's the largest Covenant fleet I've ever seen ... the largest anyone's ever seen."

High Charity appears

Cortana: "Get inside the temple and kill Regret, before it can stop us!"

{Gameplay}

Pvt. Chips Dubbo: "Man! Look at the size of that thing!"

As the Chief enters the temple

Cortana: "The Covenant fleet has launched multiple waves of Phantoms. Too many for me to track ... We don't have much time. There are Honor Guards all over this place, watch your back."

When you enter the throne room and look at Regret.

Cortana: "There's the target, take him out!"

After the Chief enters the "throne room", the Prophet talks to you.

Prophet of Regret:

"Your very existence offends me, Demon!"

"The Great Journey will not be postponed!"

"Guards! Remove this vermin from my sight!"

"Human filth, you confound this sacred place?"

"You dare to interrupt my sermon?!"

"Incompetents! I'll kill it myself!"

"Are my guards too much for you, Demon? (Laughs)"

"Warriors! Attack! The Demon must die."

"Surely, you can do better than that?"

"You shall not hide from me Demon!"

"Why anyone would fear this Demon is beyond me!"

"Perhaps you underestimated me, no?"

"This is the humans' greatest warrior? (Laughs)"

If the Chief waits around.

Cortana: "His throne's shielding is protecting him. Get in close and do whatever you can."

If the Chief continues to wait.

Cortana: "You've got to get him out of that throne."

Cortana: "Quick, board his throne!"

After the Chief defeats the Prophet

Cortana: "Bad news, the Phantoms are turning around. The fleet is preparing to fire on our position. We need to get out of here."

{Cutscene}

''The Master Chief is standing outside the temple, with dead Covenant bodies behind him. A Covenant ship is directly overhead. A huge purple beam, similar to a gravity lift, comes down, hits the temple, and starts getting brighter and brighter. It's obviously a weapon (likely an Energy Projector). The Chief turns, runs around a corner, and jumps a ledge, landing about several feet below where he was. He runs the entire length of the temple, as the temple starts exploding. He barely makes it off, and is flung into the water, where he slowly begins to sink with other bits of stone from the temple. Two tentacles come up from the bottom.''

Gravemind: "This is not your grave..."

The tentacles wrap around the Master Chief, dragging him down.

Gravemind: "But you are welcome in it."

01: Testament
Look up, immediately, a Drone swarm will descend upon you from holes in the roof, followed by a pair of Elites from the right. Try and get into the top right door and use your sword to cut the Elites down as they spawn. Note that one of the Elites is a Major, who you will have to lunge and finish with a headshot.

Once they're dead, another pair of Elites will spawn in the hall; give them the same sword-and-headshot technique. Often, a Major Elite will run into the hall from the outside, but he should fall just as easily.

This next area, though, can be pretty tricky. There are five or so sniper Jackals inhabiting the area, not to mention another group which will show up a bit further on. The safest idea is that when you exit the door, stop and look around for a Beam Rifle, outside the exit to the right. Take out the snipers and then start working on any Elites you happen to see.

Keep going and you'll run into a number of Grunts and Elites guarding a bridge. If you've taken out all the snipers it shouldn't be TOO difficult. If you haven't taken them all out, however, expect to have a Beam Rifle shot at you, so be sure to double-check the area before engaging. When you get to the far side, there will be one Elite Minor in the outer wrap-around hallway, then a room full of Grunts and Jackals all armed with Plasma Pistols; it's not hard to kill them all if you stun them with one shot and melee them to death (to save precious ammo). If you are using a Carbine or want a Carbine at this point, there's a pile of blocks semi-blocking a walkway outside. You can jump on and crouch-walk-through, and there are two Carbines (pick up one and snag the ammo of the other) and two Plasma Grenades if you're running low.

Hold on to your Beam Rifle; there are a LOT of sniper Jackals and a couple Elites in the next area, but it's next an open, so they don't have a lot of cover. Take out some of the snipers and one of the Elites (likely a Major) from the cover of the pillars just outside the Jackal-Grunt room, then close in and just melee the rest of the sniper Jackals and kill the Elite Minor (sticking is recommended, it's really easy to). Switch your Beam Rifle for one with more charge and head back through the doorway where you entered the open area. In a second, a Phantom will pull up and drop off two Hunters. However, with your new Beam Rifle, you should be able to put out two shots before they react. You can either choose to kill one of them or wound both.

Alternatively, in the very first room of the level, you could kill all the enemies, circle around to the left upper level, jump on top of the pillar that should be holding up the roof, jump over to the ledge above the door you came in by last level; from there, grenade jump up onto the ramp; from the top of the ramp, grenade jump onto the roof; from there, grenade jump to the far area with the five snipers. The bad thing about this is that it cuts you three grenades and puts you in a pretty bad position to deal with the snipers and Hunters. Oh well.

Once you have taken out the Hunters (for which I recommend taking the shotgun from one of your marines if you haven't already, a Pelican will show up, dropping reinforcements as needed, as well as a few weapon pods. At this point, give your Marines sniper weapons, and prepare to face the motley crew of the gondola, which consists of a Lance and an Elite + 2 Jackals. At the range you have, they shouldn't pose much of a threat.

Once the gondola is secure start transferring weapons out of the drop pods and into the gondola. You are going to be wanting as much firepower as you can get pretty soon.

02: One Way Ticket
Soon, a Drone swarm will buzz in to attack you from behind, but the sniper Marines will make short work of them. The gondola that passes you, however, also has a Drone swarm to complement the two Elites on board, so you may want to chip in there.

As you approach the far side, you could elect to sword-fly up to above the entrance, using the turrets, but I wouldn't advise it; the gondola will not dock if you do so, and that means losing your Marines. Therefore, I find it works better to just exchange your beam rifle for a shotgun and use it to blast your way through the next area. There are two sniper Jackals and seven regular Jackals, not to mention a Drone swarm which will spawn further up in the room once you've killed the Jackals, but they shouldn't prove too difficult for a grizzled veteran of Outskirts.

Once everything in the room except you (and hopefully a Marine or two) is dead you should walk up the ramps to the top of the room. On the platform outside there is a grunt and a Fuel rod cannon, good for later. An elevator thing will show up with some foolish Jackals inside. Plasma grenade time! (Or instead if you don't have a plasma grenade or want to conserve some, a glitch allows you to shoot through the window on top of the elevator, so use your carbine or battle rifle to headshot the Jackals inside) Once the elevator is clear (or strewn with Jackals' corpses, as the case may be), drop the shotgun in favor of a battle rifle, then step on in. We're going down.

You wind up in an underwater room with a bunch of Grunts running around. This is what Cpl. Locklear would call "an honest-to-God turkey shoot", I guess. Empty the battle rifle into them.

The next battle is full of bleh, in my opinion. Each of the two sides of this room are occupied by Jackal snipers galore, a Drone swarm, and waves of Honor Guards from doors on the lower level. To make matters worse, a team of Elites and Jackals will emerge on the upper level soon after you kill the snipers, and don't even get me started on the friggin' Hunters. So, of course, we will skip it. Head up the right side of the battle (there is a very rare possibility that the Drones will not spawn if you head up the right) and keep going straight until the floor drops of into an area with two doors onto the floor. Run out the rightmost one and head for the exit. The Hunters will generally fail to notice you if you're fast enough. Indeed, they won't even notice you jumping over their heads sometimes. If you saved the Fuel rod cannon from before you can use it to blast the Hunters.

If you really want to stick 'round and fight things out, I'd suggest saving beam rifle ammo whenever possible, using cover to its fullest, and being very, very careful. And don't expect that by sticking around you'll save your Marines: even when it looks like you've won, the Marines will manage to kill themselves in some inane and non-heroic manner. Go figure.

The next room has two invisible Elites and four invisible Grunts. They shouldn't be too difficult for you to snipe with the beam rifle. When they all die, a stealth Elite with an energy sword will show up at the far end of the room. Shoot him down and drop the battle rifle; from here on, we'll take our chances with the energy sword.

Whew. Moving on, enter the elevator and head on the next leg of your journey. At the end of the ride is a foolish Honor Guard patrolling in the other direction. Bop him in the back and kill him dead. Another Honor Guard, this one with a plasma rifle, leads a Lance down the next hall, so take them out with sword and grenades. Next, we'll be back outside, facing four Drones, three or four Jackals and two Elites. Be sure to snipe the Drones first. I don't know why, but the Elites and Jackals will often retreat once the Drones fall. At that point, take out anybody still visible with the sniper before moving in with the sword and chopping them up.

Again, the Pelican will show up once you're done. One wonders why, again, he doesn't just pick you up and drop you off at your destination, which can be barely five hundred meters away. At any rate, he'll drop you some more Marines and weapons. Hand off your beam rifle to one of the Marines; that should leave one Marine with a shotgun, which will be fairly handy for him in the next area. Grab a sniper rifle. This next area is more or less the last conventional battle in the level; after this, we have an encounter with a sniper, a defense against some Banshees, a battle against a Grunt AP team and some Ranger Elites, an assault on an entrenched position, and a constant tango with Honor Guards as we fight a boss battle. So, enjoy normal combat while it lasts.

As you move into this area, a Jackal sniper will be ahead of you. Stick him with a grenade and drop off the path to the left. As you move around the left, a Grunt will show up in front of you; beat him down with the rifle. Jump up onto the ledge, take a right, and then drop back into the main battle, where two Jackal snipers and an Elite will be trying to focus on your Marines. Disrupt their concentration with the sword. Actually, the shotgunner will often take out the Elite if you handle the snipers. Very good work, Private! You'll get a gold star! Your first Elite; I'm so proud of you!

Once the Covenant here are dead, your Marines will hopefully have survived. Jump out of the pit area and up onto the big rock facing the lake. A Phantom will soon arrive from that direction. The rock provides barely adequate cover from it. As it moves over the pit area, you'll see it drop a trio of Jackals. Leap up and lob a frag grenade into the spot where they land; with luck, they'll never hit the ground. A trio of Grunts will follow. Give them the same treatment, then drop off the rock and head for the hills, as your shield has taken a beating from the Phantom by this point.

Drop into the pit, bust out the sword, and use it to finish the two Elites that dropped from the Phantom while you were getting over here. Then jump up onto the fallen pillar to your left. There will be a space through which you can jump to get to the next area. The Marines can't follow you through here, but that only means they have to take the long way around, giving you some stealth time. There's a Jackal sniper hidden among the crates here, but the sword will end his reign of terror. Whew. On to our last gondola. This gondola is the site of two and a half battles, and they're all fairly tricky, so stock up on guns. Get all the shotguns, energy swords, plasma pistols, sniper rifles, rocket launchers, beam rifles, battle rifles and carbines that you can find onto the gondola. Then, give your Marines sniper weapons (preferably ones low on ammo, so you don't have to use them), grab the rocket launcher instead of your sword, and take off. Almost immediately, two Banshees will show up behind the gondola. As they are so lethally damage-dealing, you'll want a bit of cover to unleash the awesome power of the tracking rocket on them. Two rockets each should do the trick.

Soon, the other gondola will show up, heading the other way. There are two ranger Elites and four Grunts here. Two of the Grunts have fuel rod cannons, so I'd suggest boarding the other gondola, using the rocket launcher's remaining ammo to clear a path, and close with the fuel rod cannon Grunts before they can deal much damage. If you did this in vidmaster-perfect style, you should have gotten one or both Rangers confused enough that they're just sitting and staring at nothing--easy targets for a skilled sniper like yourself.

If you're feeling a little OCD about firepower, you could grab the fuel rod cannons in exchange for your spent rocket launcher, but I doubt you'll need it. Once everything on the far gondola is dead, hop back on to your own and continue. You have but two battles left on your arduous journey. The next one is actually remarkably pleasant, but the one after that is boring, difficult, drawn-out and contrived. Feh. Guess we gotta make do with what we get.

As you approach the temple, you should probably get rid of the rocket launcher, empty or not, and pick up a carbine or battle rifle--whichever you have more ammo for. There are a couple of Grunts mounting a defense outside the temple. Slaughter them, and they'll panic and run. However, they will soon return, having enlisted the aid of two Elites, two turret Grunts, and two Jackals. Use this battle well, as the fun is pretty much over for now.

03: Sorry, Were You In The Middle of Something?
Actually, Regret doesn't seem to be in the middle of something. One could question why he's actually here. Other than to give us an unreasonable and irritating boss fight, of course.

Head inside, swapping out your beam rifle or sniper rifle for a plasma pistol; it's noob combo for great justice here. As you do, watch out for the bottom level; two Elites will spawn there, but should fall to the noobish might of your overcharge and headshot. Once they fall, the door on the top level will open and reveal a Grunt or two and a pair of Honor Guards, swords in hand.

Kill them with the noob combo as needed.

Here, I'll insert the valuable (and wonderfully entertaining) notes of Mike Miller on this fight: "At first glance, it seems that the Prophet plagues us with the very same elements of video-game-boss cheesiness as the heretic leader (for all the good that it did him):
 * Endless supply of disposable henchmen. If you've tried sitting back by the entrance and eliminating all of the opposition in the room before moving in (which is probably the logical course of action), then you already know that it's impossible. This time, the designers don't even bother with the tenuous device of the holograms. The grunts and elites apparently just materialize directly from the Great Beyond, the grunts throughout the main area, and the elites in their little bare stone rooms with only one entrance (there are two such rooms at both the front and back).
 * Arbitrary invincibility. The prophet's floating chair apparently comes equipped with the Standard Boss Defensive System with Only One Weakness. In this case, the weakness is being punched in the face. Curiously, though, he'll scream in pain and even bleed when you hit him with other weapons, but he won't actually take any damage, even from the sword (you can sit there and swipe away at him with the sword as long as you want, but he won't die). So, don't be deceived: I've yet to find a way to kill him other than the intended method of boarding his chair.
 * Improbable avenues of movement. Like most high-ranking video game bosses, the Prophet has the ability to teleport at will. Apparently he didn't read the manual for his chair very carefully, or it just didn't occur to him to teleport up to the ceiling where you couldn't reach him.

Regret is pretty tough, but pretty stupid. His general strategy is to whine at you in his irritating voice, fire a lethal blast from his gravity beam cannon whenever you stand still too long, and teleport from one side of the room to the other every so often. You have to press X to board his chair, then B five times in a row to smack his face around. You need to deliver twenty-five punches to kill him, which is a bit tricky, especially given the fact that infinite quantities of enemies will try to stop you and he himself will teleport away every five hits (or five seconds).

Note: You can kill the Prophet of Regret in one go if you manage to board his throne and just manage to land a sixth punch right before he teleports away. You only have to board his throne once if done correctly. This has worked on a few occasions.

Interestingly, this is not the fastest (or only) way to kill Regret. Robert D. Perez has shown those of us with good trigger fingers a quicker way. Note that this is the only way to kill Regret when the Mythic Skull is active (he is talking about Mythic here): "I’ve jumped (boarded) on the Prophet of Regret’s throne exactly 48 times, say again 48 TIMES!! And each jump consists of five melee attacks. All to no avail. The bastard still lives! It was hopelessly disappointing and painfully frustrating to go back to square one after ALL those efforts. Then I simply thought of something out of this inevitability; what would the Master Chief do in a circumstance such as the one I’m overwhelmed in. Surely there has got to be another way, instead of the 48 plus jumps and five melee attacks per jump. I collected my thoughts and recounted the options I had, had another hard look at the weapons at my disposal.

It then hit me! Nothing can penetrate his immensely resilient force field. Other than the fact that once you jump on him you have the advantage of striking him with your melee attacks. So what to do? Well, it is quite simple; you throw a Plasma Grenade or a Fragmentation Grenade on him a split second before you board his throne. Picture it like this, your throwing arm penetrating his force field before you throw the grenades, with this objective the grenades will land or stay inside his force field. Therefore it is important that you throw the grenades inside his force field before you are unable to do so when you board. Remember that our Master Chief cannot throw or use his weapons when he has actually boarded the throne. Adversely if you throw them too early they will not stick or stay inside the force field. Or as in the fragmentation grenades case they’ll simply rebound off his force field, thus musing the already contempt Prophet of Regret. At other times, if you are unlucky the plasma grenades will also bounce, though feebly off his force field and may end up adhering to you instead, a big no-no to avoid. So you MUST throw the grenades a split second before you latch onto his throne and not a moment too soon.

If done correctly the Plasma/Fragmentation Grenades will drop inside his force field and not fall off. The resulting explosion will then knock him hard, so for added effectiveness commence punching him straight afterwards or before the explosion (you’ll only land in two or three punches, as shortly afterwards he’ll teleport in a fragile panic).

Don’t worry about getting killed or damaged by the plasma grenade since the explosion occurs inside of his force field. It will not harm our Master Chief. Just be sure to throw the grenade before you press and hold on to the ‘X’ button with which to board his throne. If he is at a higher elevation than you are at, then all you need to do is press the jump button, throw the grenade and then board him. This is simply a brilliant tactic on Bungie’s forward thinking. You will need to do this about six times to finish him off entirely or maybe more if your grenades do not fall inside his force field. Use your EARS to listen and to home in on the direction he’ll spawn to next. It’ll guarantee and reward your efforts with a far better success rate. Your radar is your best friend in these given circumstances, as the battles to follow are hectic to outwit.

You can also drop the grenades inside his force field without boarding his throne. Run up very close to The Prophet of Regret’s throne and throw your grenades at point blank. If done successfully the grenades will drop inside his force field. Please note that this method will not yield the desired effects on every attempt as it is at times hard to judge how close you are to the Prophet of Regret. Amidst all the battle commotion and pandemonium it is especially harder to pull off.

Lastly, don’t forget to PATIENTLY take out the re-spawning Honor Guards as well as the Grunts who’ll make certain of your efforts being anything but a success. Take them out before engaging the Prophet of Regret. The best way of doing this is to run back up the side ramps and look out for them on the top level. Check your radar as well if you cannot see them from this higher elevated vantage point. And lastly don’t forget to MOVE! Otherwise the pesky but cute little grunts will find you an easy target for plasma grenade shelling."

And for those of use with slightly "less machine-like timing than Robert D. Perez", Sid Fleischmann has posted another possible tactic.

"I found…easier ways of doing [the Regret boss-fight] that are much quicker [than normal strategies] if you do them right. First is done by yourself. You need an [energy] sword and for mental aid, a plasma pistol. The pistol is for the elites, all you do is overcharge and slice. Now for the Prophet. Lunge at the prophet, and board the second after you 'hear' a successful hit. You will apparently board and cut him at the same time! This can even result in one hit kills!"

Indeed, both strategies work, and are far quicker than the normal way. However, since both require a decent amount of luck, it is generally safest to use the noobish but deadly strategy I've outlined above.

Another strategy you could use involves the rocket launcher. When you get into his throneroom, make sure you have at least 2 rockets left. Go in, lock on to his chair from the ledge in front of the entrance, and fire the rockets. After both rockets have hit their target, jump onto his chair and punch him to death. It will only take about 2 punches to kill him.

Once that jackwad finally goes down, watch the pretty cinematic. Congratulations are in order.

Different Ways to Kill Regret
Method 1: Boarding The following method is the most commonly practiced and also possibly the easiest method. Board his throne. Melee him, (the same way you hijack a vehicle) until you're thrown off.

Method 2: Energy Sword The second method involves using an Energy Sword. Get an Energy Sword. Go inside his temple. Board his throne. Beat him twice. Get off. Slash him with the Energy Sword (immediately after you get off of him).

Method 3: Go near Regret's throne. You need to be close enough for the plasma grenade to explode at the proper time. Run up to a wall and throw a plasma grenade at it so it bounces off and sticks to you. Board his throne as soon as possible, you must board his throne before the grenade detonates. The grenade will detonate and you will die, but if you listen, you will hear the Prophet of Regret scream as though you have killed him. This method should also kill him. It is unknown why this happens, as all other attacks do not harm him at all; however, it's not very useful.

Method 4: Throw your plasma grenade at him. Board his throne immediately after throwing the grenade. The grenade will be "inside" his Plasma-Shield. It won't kill him, but it will cause a lot of damage - and you won't be hurt. Fragmentation Grenades work as well.

Glitches

 * It is possible to skip the whole first part by grenade jumping. When you start, grab a Marine's Battle Rifle, leave the room, stick the Elite, and grenade jump to the tower at your right. Grenade jump to the gondola and hop to the stairs. Enemies should spawn next to you and the gondola will start to leave. Grenade jump onto the gondola (this may take a few tries), then hop to the next coming gondola and go.
 * When you ride the final gondola to Regret's area, if you grenade jump to the area before the gondola extends its docking bridge, you will get the cutscene of Master Chief walking on thin air where the bridge should be. After it is over, the bridge is still gone, trapping the Marines on it.
 * If you have the Sputnik skull, you can flip Regret's chair over. Unfortunately, he immediately teleports and gets back in. If Regret dies right after his chair gets flipped over, he'll clone for a moment.
 * When the underwater elevator of the first structure starts coming up you can throw a grenade at it and all the Jackals die even though the grenade was on the outside of the elevator.
 * Also in the underwater elevator part if you press the activation switch and get off quickly the elevator closes and go down you will reappear inside of the elevator.
 * If you have a dead Jackal on an underwater elevator press the activation switch and sometimes after the ride ends if you look at the Jackal he oddly turns blue. '''Note: this only happens a few times, and that this glitch is common to what happens when a jackal is dead in a Scarab they turn different colors.
 * When you are in the first elevator it is possible to get out of the elevator and walk about underwater.
 * It is possible to fall into the water during the elevator ride, though this will kill you at once.
 * If you acquire an Energy Sword and aim the reticle at a hologram of Regret, you will lunge at him if close enough.
 * When the Pelican drops supplies, if you are standing right beneath one of the weapon pods, you will die.
 * If you start the underwater elevator and quickly exit it, it will still descend and the player will be teleported back inside shortly after.

Mistakes

 * When the fleet jumps in, the noises the jumps make travel at many times the speed of sound. There should be a delay.
 * After the cutscene where High Charity appears out of slipspace, look up. High Charity will no longer be the same size as before.
 * On rare occasions while traveling in the sea elevator, one or two fish will swim right in and out of the elevator.
 * In the courtyard with the fallen pillar, you can actually fall through the floor. If you have this level's skull, try to beat the Covenant coming out of the Phantom from the other side of a rock. If done right, you should fall through and the rock will be floating in the sky! (Note: you may need to be walking into the rock as you hit the Covenant for this to work).

Easter Eggs

 * The Assassins Skull can be found on this level.
 * When you play this level on lower difficulties, you can find the Assassins Skull, in the same spot as it is on Legendary. You can pick it up but its effect will not activate.
 * Before the Jackals come up on the underwater elevator, if you walk up the ramps, you will find a lone Grunt sleeping next to a Fuel Rod Cannon.
 * On the area where you have come out of the last underwater elevator, there is a stone courtyard with a fallen pillar on it. In this courtyard is a stone sofa.

Miscellaneous

 * Once all the Drones, Jackals, and Grunts are eliminated and taken care of, the elevator will actually spawn more Jackals and make its way up. Make sure you're looking at it when the Jackals spawn and throw a Plasma Grenade onto the top of the elevator before it starts up. This should kill all the Jackals with an impossible grenade throw with minimal effort.
 * When on the Gondola to the Main Temple, two Banshees will attack, however it is not possible to drive them. Even if you do manage to kill the pilot and have it land on the Gondola in one piece, you still wouldn't be able to drive them.
 * An alternative and very quick method to kill Regret is getting into melee range, sticking him at the body with a plasma grenade and then boarding him. You should have Regret killed in a short amount of time and the plasma grenade will not harm you.
 * If the Marine stands on the elevator instead of inside it, when the elevator gets into the water, he/she will die.
 * Before you start the Gondola (either one), you may want to store some weapons on it. Unlike the bodies on the Gondola, any weapons you place on them will not disappear. Ones that the Covenant soldiers drop will, however, so switch their weapons for the ones you want to bring with you on the Gondolas.
 * You can see the Sentinel Wall in the distance, implying that the area is pretty close to the Library.
 * If you begin this level after just playing the previous level, both Marines that join you at the beginning will have SMGs. However, if you just started the level, one of the Marines will have a Shotgun.
 * It is impossible to kill all the Grunts in the Prophet of Regret's chamber, as they will constantly respawn, but there is only a certain amount of Elites depending on which difficulty you are playing.
 * If on either of the Gondola rides, you jump over to the other one that stops next to yours, after the Covenant are dead, your gondola won't move until you are back on it.
 * The Prophet of Regret will never teleport to the same spot when you’re fighting him.
 * This is the first level in the Series Gravemind is mentiond.
 * This level includes another music piece not featured on the soundtrack, at least not the in-game variation; it is played at the first gondola landing after you kill the Hunters. It is similar to the choral movement of the Sacred Icon Suite, but has more orchestra instruments. After you kill the enemies on the gondola, it segues to the drum solo from later in the suite(which is right after the Orbit of Glass part on the soundtrack).

Images
 Image:Ship4.jpg|Chief escapes... Sort of. Image:Covie1.jpg|High Charity and the Second Fleet of Homogenous Clarity coming out of Slipspace. 