THE FLOOD
Halo: Fireteam Raven also gave us a bounty of awesome encounters against everyone’s favorite ancient evil parasite. In addition to the usual suspects (Keyser Söze not included), the FTR experience added a few new surprises into the mix.
PURE FORM
Even from the reveal trailer folks were asking, “wait… did I just see a pure form?!” Deep-lore denizens who went zero-to-Incredulous Hulk in 3.43 seconds found their curious consternation centrally steeped in the fact that, under normal circumstances, the presence of a Gravemind is typically required for the creation of new pureforms. Which, to be clear, is still largely the case (biomass joke).
That being said, the appearance of a pure form during the conflict at Alpha Halo is not implausible or impractical. Aside from just being a cool enemy to fight from a sheer gameplay perspective, there’s preexisting lore precedent as well. We’ve actually already seen examples of pureforms kept in containment areas of a Halo ring as far back as a decade ago, when the Cold Storage map was released for Halo 3.
As the Flood consume and convert everything in their path, the lack of potential hosts soon limits its ability to create new infected. However, with the conversion of the environment and the existence of a centralized intelligence, the Flood can spontaneously generate new war-forms entirely from FSC (Flood Super Cell) and salvaged skeletons. The variety of forms that these creatures take is vast, and nearly impossible to effectively catalogue; particularly as many can change to another configuration in response to new threats.
JUGGERNAUT
Speaking of big surprises, quite literally the biggest one was likely the appearance of the fabled Flood Juggernaut combat form. Ever since their removal during the development of Halo 2, the Juggernauts have been theorized about and dwelled upon, with many fans wondering if we’d ever get to see them in the, well, flesh (gross).
In many ways, Halo: Fireteam Raven was perhaps the perfect place for their debut – an oversized, bombastic enemy for an oversized, bombastic Halo campaign experience. Encounters with a Juggernaut in the game is always a sight to behold, with quick responses and combined fire needed in spades.

Juggernauts are highly specialized combat forms directed by a seething mass of infection forms linked to multiple hosts. The creature harnesses the hosts' minds to analyze enemy activity and adjust the local Flood strategy accordingly. They have some of the traits associated with full-fledged key minds, including the abilities to synchronize nearby parasites and relay information between distant Flood hordes.
The most significant aspect of the Juggernaut is their enormous size and raw physical strength, capable of impaling armored vehicles with their sharpened tendril-arms and crush unsuspecting victims with their trunk-like legs.