Who Or What Is the Plague?

{mosimage} Frenzy_Rumble's gotten his hands on the Blu-Ray of astf, and while searching through the special features, he made a discovery.  A scale chart of ROTF Transformers (including the Fallen, Demolishor, Ransack (!) and Earth mode Soundwave) includes a grayed out design for something labeled 'The Plague.'  It says no vehicle form, but mentions a combined form.  Who could this be?  The legion of Decepticon Protoforms perhaps?  Or a new figure we have yet to see?  Scope out the image here!