

Additionally, these enemies will often sneak-up on the player - this can result in quick kills.

The Flood are generally annoying to combat after large fights depleted shields are likely. They are best taken out at range, since their melee attack can remove shields with two hits (normal), or one hit (Heroic and Legendary). The Juggernaut can take a tremendous amount of damage, about 4-5 Energy Sword swings or 3-4 rockets. Once the Pure Form turns into this living tank, it usually can't/won't turn back. Juggernaut form: Rivaling the Covenant Hunter in it's size, this form is undeniably the strongest form of The Flood.These forms are inclined to stay in groups, firing all at once, or at different times as to pin the player into a single area of cover. Ranged form: Usually after the stalker form sees the player, it then crawls to a high ledge, or even a ceiling, and will fire relentlessly in the form of sharp needles.They usually do not attack the player, unless the player is standing in their way however, they can do serious damage to unshielded players. Stalker form: These Insect-like creatures are very agile and can jump huge distances, they can also crawl on walls.Only featured in Halo 3, this creature is capable of shifting between three forms Pure form: An Elite wielding an Energy Sword stands over a Flood combat form Not only does it kill the carrier, but it can be done at a distance and it often kills all of the spores that the carrier releases. A carrier can easily be destroyed, along with ALL of its spores, with a simple Plasma grenade (or incendiary, but they are extremely hard to find). These are huge, bloated, slow-moving Flood that try to kamikaze the player, exploding when shot or when close to the player, and releasing an explosion that does significant damage and a wave of Infection forms. They are formed out of Elites, humans, or Brutes, and are highly versatile, capable of using a variety of weaponry in addition to their deadly melee attack, using equipment such as shielding and cloaking, and even piloting vehicles. These are the foot soldiers of the Flood. From Halo 2 onwards, they can reanimate killed Flood corpses, and in Halo 3, they can reanimate any human, Elite, or Brute corpse instantly, they can also reanimate flood corpses unless the legs, arms and body are melee'd/shot at enough. They often attack in huge quantities and can do fatal damage to Master Chief if his shields are down. The most basic unit of the flood, this small creature is known as a 'spore'. Once infected the host can be evolved and twisted into fighting units, some of which can use weapons, or swollen up to become essentially another egg sack to breed new parasites. Its purpose is to infect any sentient life it comes into contact with.

The Flood has many forms, but begins as a small parasite born from an egg sack.

In the bestiary booklet that came with Halo 3, it is revealed that the Flood utilize a special type of cell (Flood Super Cell) which can be described as a 'thinking muscle', and can be rearranged to resemble any necessary organs. Many species were also preserved and kept safe by the Forerunners so that they could later evolve and restore life to the galaxy, although the Forerunners still decided to sacrifice themselves. It was decided that destroying all sentient life in the galaxy (thus denying The Flood any source of food or sentient life to infect) was more practical than the conventional methods of control that were already failing. The story revealed that this parasitic creature probably came from outside the Milky Way galaxy, and was what caused The Forerunners to construct the Halo arrays in the first place. As an unexpected addition to the original game, The Flood became Master Chief's true foe in the Halo series.
