The Flood is the ninth level of the real-time strategy game, Halo Wars. As Spartan Red Team tries to locate Professor Anders' signal, their Warthog is destroyed in a crash, leaving them separated from the main UNSC force. Under orders from Captain Cutter, Sergeant John Forge mounts a force to assist the Spartans from a nearby UNSC base. Soon, however, the UNSC forces encounter Flood colonies scattered about the landscape, and a Flood Proto-Gravemind. Serina informs the UNSC forces that the Proto-Gravemind may be the reason they are unable to get a fix on Anders' signal, and all UNSC ground forces are rerouted to destroy it.
Red Team's Warthog is moving at high speed, shooting at enemies.
- Jerome: "Spirit of Fire, this is Red Team. We are 100 meters from Ander's transponder signal... Meeting strong resistance. Seein' some pretty crazy stuff out here, over."
After the Warthog crashes, the Spartans continue on foot.
- Captain Cutter: "Hold your position, Red Team. Reinforcements will come to you."
- Captain Cutter: "Sergeant Forge, rendezvous with Red Team and find Anders, but be careful: we don't know what these things are capable of."
- Serina: "I've received Red Team's coordinates. I've marked it on your map."
When several minutes have passed:
- Jerome: "Spirit of Fire, getting a little hairy here, sir. Where's that backup?"
After the player has destroyed the first Flood colony:
- Jerome: "Not sure what just happened, but the large one just shook like it was hurt."
- Serina: "Yes - when the colony was destroyed, I registered the large creature weakening."
- Jerome: "We noticed a few colony creatures on the way in. We can weaken the big one by taking them out first. Uploading coordinates."
After a second Flood colony is destroyed:
- Serina: "Keep killing those things. The big one is even weaker!"
If a Flood colony has regenerated:
- Serina: "One of the colonies has regenerated and the large creature has gained strength."
- Marine: "Regenerated? Why can't these things just stay dead when I kill them?"
When the player's units move near Red Team:'
- Jerome: "About time you guys showed up!"
- Serina: "I've lost Anders' transponder - could the creature be jamming the signal?"
After the Proto-Gravemind is destroyed:
- Marine: "Yay, all of the creatures are dying!"
- Captain Cutter: "Serina, report. What's going on here?"
- Serina: "Captain, as soon as that creature died, I picked up a new signal just east of here."
- This is not the first level to feature a Proto-Gravemind, as one was seen in the level Keyes from Halo: Combat Evolved, but it is the first level in which the player must destroy one. In the objective menu, it is referred to as the "Flood Boss".
- The Warthog that Red Team are driving in the opening sequence differs from the normal model, it has a much darker color and is wider. This could be a special model made for the Spartans, as they are much heavier. The Warthog in the sequence looks like a Spade in Halo: Reach.
- At the start of the level, when Red Team is riding their Warthog, one of the Spartans (most likely Jerome-092) is shooting a sniper rifle, but once the Warthog flips, all three Spartans have their normal weapons (Alice 130 - chain gun, Douglas 042 - rocket launcher, and Jerome 092 - Spartan Laser).
- While a Marine cheers "Yay, all the creatures are dying!" when the Proto-Gravemind is killed, the subtitles report that he instead asks Serina what is going on.