Promethean Knight

The Promethean Knight is an advanced Forerunner sentinel that appears as an enemy in Halo 4. They deploy Watchers from their carapaces in combat, which increase the survivability of Knights in return.

They have two large robotic arms, which wield weapons, and two, smaller, micro-driver arms below the two robotic ones. They can be armed with every Promethean weapon but are most commonly seen using the Light Rifle, Scattershot and Supressor.

There are several variants of the Promethean Knight which fill a wide spectrum of battlefield roles. At least three variants made an appearance in the E3 2012 gameplay demo - the first encounter showcasing the basic Knight, the second, a Knight Lancer, and a Knight Battlewagon in the final in-game cutscene of the demo. They seem to be the Promethean equivalent to an Elite.

The Prometheans are, in actuality, ancient Prometheans and Humans altered by the Composer to give them a mechanized body, immune to being used by the Flood, as the Flood can only infect living tissue. The first Knights were the original Prometheans but these were too few in number, so the Didact turned to his old foes, humanity. He began to "conscript" groups of humans meant to be indexed in preparation for the activation of the Halo Array, gaining at the same time increased numbers for his army and a measure of retribution for humanity's actions during the Human-Forerunner war. A group of Forerunners however, saw what the Didact was doing, and because of their belief in the Mantle of Responsibility imprisoned the Didact and shut-down the project. Becoming AIs, they gained a rampant-like quality, becoming just like sentinels to serve under the Ur-Didact.

Knight Lancers
A variant of Promethean Knights, Knight Lancers act as scouts and marksmen, using Promethean Vision to track their targets. In line with their role as scouts, vanguards and snipers, they are extremely accurate even at long range. Lancers are able to charge the player in a zig-zag like fashion by teleporting in quick succession, rapidly closing the distance between themselves and the player where they can bring their Light Rifle or Binary Rifle, and Blade Arms to bear. Lancers are distinguishable by the large angular pieces on their back armor.

Knight Commanders
Knight Commanders lead groups of Promethean Knights. Accordingly, they are able to bear Incineration Cannons, boast stronger armor, and can deploy floating Autosentry turrets to further distract and overwhelm the enemy. They also have an ability that allows them to push anything in front of the commander away and to push itself in the air. It is not yet known how commanders do that. Commanders are distinguishable by their yellow markings on their face and back armor.

Knight Battlewagon
Knight Battlewagons were rarely seen in the field, being deployed only when other Promethean forces had failed. In addition to the abilities of the Knight Commander, they boast additional Hardlight shielding and utilize the Scattershot, making it a real challenge to even get close to them. Battlewagons are distinguishable by their large hardlight spines as well as the same facial markings as the commanders albeit a darker shade of yellow.

Tactics

 * Prometheans are among the most difficult enemies faced in the entire Halo series. Although their large size presents a larger target they compensate with their ability to teleport, which they do at random. Their shields are strong and are able to ward off large amounts of damage. Their considerable strength also makes them risky to approach in close quarters as their melee attacks are devastating. Only Sangheili and Jiralhanae can compare on levels of damage.
 * Their difficulty is compounded even further by the fact that they often lead groups of Promethean Crawlers into battle which often flank the player and flush them out of cover for the Knights to attack.
 * The Promethean Watchers that they deploy are capable of offering support fire for the Knights as well as protection. They can project a Hardlight Shield to protect Knights from damage, can catch thrown grenades and throw them back at the player, and can regenerate fallen Knights.
 * The Gravity Hammer is an excellent weapon against the Prometheans. A direct hit can kill all Prometheans in a single strike on lower difficulties and severely damage them on higher difficulties.
 * The Noob Combo is probably the most useful way to dispose of all Knight classes, provided that you have a Plasma Pistol. Once you deplete the Knight's shields, keep on spamming headshots to their exposed skull with any precision-class weapon (Battle Rifle, DMR, Light Rifle, etc).
 * A variation of the Noob Combo (replacing the precision weapon with a Plasma Grenade) will instantly kill any form of Knight on any difficulty, making this the easiest way to dispose of them. Usually, when a Knight is struck by the charged plasma shot, it will be stunned, leaving a short window to stick it with the grenade. This tactic, however, can prove ineffective against larger numbers of Knights (due to the fact that each player can only carry two Plasma Grenades at any given time), but it is very useful against single Knights wielding a Scattershot or an Incineration Cannon, even on Legendary. This strategy becomes more effective in cooperative play, since the number of Plasma Grenades available increases with each additional player that carries them.
 * When a Lancer begins to do a "Zig-zag Teleport Charge", start moving backwards. The Knight's lunge targets where you were standing when it initiated that attack, and if you don't move you are likely to be killed (especially if your shields are not 100%).
 * A Lancer will always teleport away after a Zig-zag Charge, but will pause for just a second before it does. If you have a Shotgun or Scattershot, you can kill it before it teleports away (on lower difficulties) or heavily damage it (on higher difficulties).
 * The Shotgun and Scattershot are good weapons against the Prometheans. Even on Legendary, only 3-4 shots should be required to kill them.
 * Once their shields are depleted fire once into their face with a precision weapon. A small, glowing, circular hole will open on the front of their face, shooting into this hole with a precision weapon will kill them instantly.
 * An effective exploit to use on Easy, Normal or sometimes Heroic difficulties is to melee a Knight while strafing around it until you are in the position to perform an asassination.
 * Knights are quite surprisingly resistent to the Railgun, however due to the extreme amount of damage it inflicts it will still usually kill it in one hit. This resistence is however noticeable by a great deal on Heroic settings or higher with the Tilt skull activated, where it takes anywhere from 2 to 3 fully charged shots to down a single knight, so it is not advisable to waste its valueable ammo unless absoulutely necessary under these conditions.

Trivia

 * Based on observations made during combat where one knight exposed its skeletal "face" to John-117, Cortana believes that the Knights are memetic in nature.
 * It is interesting to note that only their small manipulator hands are connected to their bodies. Their weapon arms and legs float free from their body. Despite this, the legs still seem to support their weight as opposed to some form of anti-gravity device as the body sways and moves in response the the Prometheans' heavy footsteps.
 * Their manipulator hands have five digits; it is unknown if these Knights were originally human, or if they were Prometheans who have not undergone the same mutations as the Ur-Didact.

Appearances

 * Halo 4
 * Halo: Silentium