Reposting my Faction Sheet for convenience:

Faction Name: The Flood
Universe: Halo
Summary in a Sentence: You ever have a nightmare where you get eaten by a monster, and then become that monster? No? Well good, I wouldn't want to spoil the surprise.
Description: Far beyond the reaches of the Milky Way Galaxy a threat loomed on the horizon, an army of flesh and bone and bloodshed. Possibly so powerful to have wiped out galaxies in its wake, only the Precursors could stop them. A technology so advanced met heavy resistance, but eventually The Flood were defeated. Later to be revived by the ancestors of man, The Flood were free to wage war against all existence again. The Forerunners were barely capable of creating a tool to destroy them. At the cost of their own lives. But again, the hardy Flood rose again, and they set their eyes on Mankind once more. 

They feed on the bodies of their enemies, countless in number and ranks. The Flood consume what opposes them and turn them against their allies, absorbing their biomass into a great consciousness. The Gravemind learns all that its children consume, The Gravemind know all from the past. With its knowledge and connection to its loyal army, the Gravemind is a horror to truly behold. Even without its armies, The Gravemind is more incomprehensibly dangerous than can be easily described. Its mind is so great in power that it can impose its will upon the living in close proximity. 

All who oppose The Flood shall be consumed, atonement for the sins of the father.
Technology Level: Varies depending on who they absorb into their ranks.
Other:
Important People: 
+Name: The Gravemind
+Role: Quite literally the brain of the Flood.
+Description: A gargantuan amalgam of flesh and bone, ancient in body and mind. Millions of bodies fused together into this hulking growth. It oozes a thick fog with every breath, a toxin so great that if inhaled will convert you to a flood in moments. It is serpentine in form and riddled with appendages formed throughout the ages. It is a rotten festering monstrosity, and even in its disgusting and inhuman form. It is still capable of locomotion if necessary, if roused from its static position it measures incomprehensibly long. Its body once filled all of the halls of the Halo ring it laid in. 
+Brief Bio: Though the Spartan thought it defeated, The Gravemind fled to another ring, and eventually to the Ark itself. The Gravemind persevered even through that. The Ark was destroyed but little did the Chief know, Gravemind and some of his legions found themselves in a new and strange world, with remnants of the Ark holding them in place. An ocean surrounded them, they had been transported by some unknown force to this new realm with new possibilities for consumption. Free from the dangers of the Spartan known as John. Though this transportation came at a price, a large portion of The Gravemind was lost in the process. Its body has lost almost 40% of its biomass, and it intends to gather much more to heal its deep wounds.

Hex Location: 4'4
Terrain Type: Flood Corrupted
Important Terrain Features: Metal structures torn and rusted, wrought with the flesh of thousands of fallen foes. It is a sickly orange and brown island 1/3 natural, 1/3 machine, and 1/3 flood. The remnants of the artificial structures of the Ark came with them, along with the terrain of the Halo rings. All corrupted by a horrid flood compound that gradually grows and spreads to fill the spaces.
Important Structures: The Gravemind's Chamber, deep beneath the remnants of the Ark lies the Gravemind's enormous chamber.
Other: In the deeper chambers are hordes of infected and pure Flood roaming and hunting for any remaining survivors. These halls are filled with a pollen that once breathed in damns you to the fate of the Flood hordes. Within moments you become one with the Flood, compelled to fight for The Gravemind.