To win, the survivors must survive 3 minutes, while the Flood must infect the survivors. Survivors are equipped with a Shotgun and Magnum. The Infected will use their claw to melee the enemy. The Flood are extremely fast and can jump very high. There are three classes for the flood; Hunter (Thruster Pack ability), Stalker (Promethean Vision ability), and Lurker (Active Camo ability). Each class has the same character model and weapons, the only differences is their class names and armor abilities.
The Flood Character Model: A unique character model for both first and third-person.
The Claw: A special melee weapon tuned just for the Flood.
Flood Armor Effect: A special effect that trails behind Flood characters.
Flood Screen Effect: A first-person screen effect that shows the haunted view of a Flood.
Dynamic Music: When playing as the Flood or final Survivor, dynamic music plays in the background to intensify the experience.
Flood Gameplay Tuning: Flood move faster, react differently to bullets, and have specially tuned armor abilities, the core of which is an enhanced Flood Thrust Pack.
Flood has its own set of unique medals, including:
- Flood Conversion: Convert a Spartan to the Flood
- Alpha Conversion: Convert a Spartan to the Flood as an Alpha
- Infector: Kill 2 Spartans in a row as a Flood without dying
- Carrier: Kill 3 Spartans in a row as a Flood without dying
- Juggernaut: Kill 4 Spartans in a row as a Flood without dying
- Gravemind: Kill ALL Spartans in a row as a Flood without dying
- Flood Kill: Kill a Flood
- Flood Kill Assist: Assist killing a Flood
- Flood Hunter: Kill 4 Flood in a row as a Spartan without dying
- Flood Survivor: Kill 6 Flood in a row as a Spartan without dying
- Flood Exterminator: Kill 10 Flood in a row as a Spartan without dying
- Last Man Standing: Be the last surviving Spartan
- Final Conversion: Kill the last remaining Spartan
- Flood Victory: Contribute to the Flood total conversion of all Spartans
- Ancient One: Survive the entire round as a Flood and convert at least one Spartan
- Clever: Survive the entire round as a Spartan
Flood mode glitchesEdit
- In flood mode, there are quite a few glitches in the gametype. In one instance, a player has joined the game as a human but just before that player chooses a class, the game finds a new host. When this happens, the player spawns with an Assault Rifle instead of a Shotgun, which can give that player a huge advantage due to the strength of the weapon and the range of the weapon. Another glitch, which has since been patched, grants the infected players the ability to pick up dead human weapons. This glitch makes the player carry the weapon in the infected claw-like arm. This gives that player a small but really useful advantage against other players.
- Another glitch can occur when the players spawns in with a DMR and appears as hostile to all other players, when killed by a Flood or player they will respawn as a player with their DMR however if they kill a human the human will turn into Flood. There is also a small graphical glitch where a player that joins in to a matchmaking game in progress will posses their default armor color, instead of the forced yellow.
- In Rooster Teeth Fails of the Weak, a glitch is seen in Volume 140 in which a player with the gamertag Drunkin Donuts (supposedly Flood team) seems to be a friendly to the Flood players, has a Flood Claw in first person, but has no visual effect, is capable of attacking Flood like they're enemies, as well as perform Flood assassinations. Both are seen when he spawns behind a Flood player when the game begins, and almost immediately assassinates them using what appears to be this assassination: |||Player A knocks Player B to the ground and then lunges at him with Player B stabbed through the left shoulder. Player A then performs a lateral slice across the right of Player B's neck that kills Player B.||| However, as there is no Flood claw to be seen in third person, this gives off the impression that the glitched player is angrily slashing the Flood player with his bare hand, then screaming in rage at them.
- The Flood forms in the game are infected Spartans. However they have a few traits that set them apart from regular Flood Combat Forms. They lack the sensory tentacles of most combat forms, the host's head is still intact (and highly modified), and their melee weapon is not only a claw as opposed to the tentacles of regular combat forms but it is also on the right arm as opposed to the left.
- For Saint Patrick's Day, all human players had green armor instead of yellow, and all Flood players had green on their "skin".