Bloodthirsty monsters created by an alien virus, the Plague exist for one thing only – to spread their contagion as far as possible. The virus affects its hosts in a variety of ways; its earliest victims become towering hulks, filled with a steadfast will which drives their lesser kin. In its second generation, the Plague creates smaller, faster, but no less deadly monsters. The third stage infected show considerably less extreme physical changes, but they retain the ability to use technology, laying down covering fire with looted weapons while their larger brethren advance.