On Keld-7, a frozen, collapsing black-budget cryogenic outpost built inside a moon, failing pressure seals and extreme cold have made the facility deadly. Fireteam Fury-Seven, an enhanced human squad, enters to recover cryo-tanks, genetic archives, and suspended personnel from Black Site Delta. An Ascendancy theocratic operative named Teyla is held captive inside, and bio-organic alien siege organisms called Sentinels anchor themselves at infrastructure junctions, seeding dormant larvae into the concrete.

The extreme cold preserves millions of dormant larvae inside the outpost's frozen walls. Teyla carries a modified neural architecture that broadcasts subsonic frequencies, and a psychic link forms between her and the squad leader. This link maps the outpost's structural vulnerabilities directly to the dormant larvae through his neural path ...