Nobody knows where the M virus started, but it tore through the city fast—most victims were dead in days, while the unlucky ones mutated. The infected were quarantined inside a bio-dome force field around Palamira, and over time the virus grew strong enough to manifest on its own as colossal creatures called Behemoths. A survivor who goes by Phoenix wakes with no memory of who she was before, but one certainty: the dome will never come down while the Behemoths live, so she will have to take them down herself.