The Flood is an alien seen in Halo
The flood is a parasite that is controlled by a creature called Gravemind. The Flood have the ability to control most sentient species. They do so by digging into the host's chest and taking control of most organs. They retain most memories from the victim, like how to use weapons.
These creatures have many forms such as these.
As the name suggests, these are the type of flood that infect the victim's bodies, making them zombies. They are relatively small and weak. They usually attack in large numbers with great speed. The best way to kill them is with a automatic weapon.
These forms of flood are the victims of the Infection forms. They have enlarged claws on one hand used for close combat, and a smaller hand for the use of weapons. They are incredibly fast, agile, and deadly. If they fall to the ground and still have there legs and arm(s) intact, an infection form can reanimate them so they can fight again. The best way to take these down is with a strong, medium to heavy weapon like a shotgun or Sparten Laser.
The Carrier form is a large, fat form of the flood. It carries many infection forms inside its body. When close to an enemy, it will fall to the ground and blow up. It then unleashes a group of flood and deals moderate damage to anything caught in the blast. The best way to deal with it is to kill it from a distance and then throw a grenade just as it blows to destroy all the flood.
These are flood who will change into either of the ones listed below to fit a combat scenerio
This pure form is incredibly fast and agile, making difficult to fight. They will jump on walls and cielings finding a way to ambush and attack you with thier giant claws. The best way to deal with thes is an automatic weapon or a flamethrower. They usually transform into stronger pure forms.