Flood pure form
From Halopedia, the Halo wiki
This is a new form of the flood that is yet to be released and confirmed. Pictures and other data have not yet surfaced except names given by those who have Halo 3 early. There are three unconfirmed sub form such as Stalker, Ranged, and Tank form. More information will become available as Halo 3 hit shelves Tuesday September 2007.