Flood pure form
From Halopedia, the Halo wiki
File:Impurity This is a new form of the flood that is yet to be released and confirmed. There are three unconfirmed sub form such as Stalker, Ranged, and Tank form.
Pure Form Stalker-The Pure Form is built within a framework of recast bone.20
Pure Form Ranged-The Pure Form creates its missiles from battlefield detritus.30
Pure Form Tank-The Pure Form is an engine of war crafted from living flesh.
Heres a link http://www.bungie.net/Stats/GameStatsCampaignHalo3.aspx?gameid=22671
