Flood Juggernaut

Summary
The Flood Juggernaut is the name given to a large Flood form found encoded in the Halo 2 disc the same way as the Engineers in Halo 1. The Flood is very large, perhaps twice as tall as the Master Chief, hence the name "Juggernaut". The Flood Juggernaut is thought to be the infected form of either an Engineer or a Drinol, and was removed from the game with its base form, although the pictures suggest that the Juggernaut is an Engineer, the legs are too skinny for it to be a Drinol. It is unlikely that the Flood Juggernuat is a Drinol due to the fact that if you look at the body structure of the Drinol you will see that it has large incubering arms while the Juggernaut does not, it more or less resembles an Engineer with it's tentacles being more numerous than a Drinol's. The only way it would be possible for it to be an infected form of Drinol is if the Flood had to Split the arms of the creature, but this is unlikely in the respect that the Flood would not change a body that drastically, it has never done anything of the sort to other infected beings.

They were going to appear in the Arbiter levels, The Oracle and Quarantine Zone. Although the model, textues ect. are stored on High Charity, There are no Spawn Points meant for it.

While some suspect it to be a Flood-infected Hunter, this is actually impossible. The Hunter is in fact a mass of sentient worm-like creatures that operate under one consciousness. Due to this anatomy the Hunter cannot become infected.

Some fans also believe it could be a combined form of several combat forms. It could also be a more mature stage of the flood, since flood do age into Carrier Forms over time, this could be the stage after combat but before carrier, hence it's shape.

One speculation is that it's a Heretic experiment since the first part of the map Oracle is called Juggernaut.