On Blackwater Station Six, a deep-sea pressure station under a corrosive ocean at 300 atmospheres, degraded seals and failing systems have created a collapsing death trap. Central Authority garrison troops are ordered down the East Pressure Spine to secure the lower pump galleries from an advancing secessionist mechanized force. But the secessionist vanguard has already been wiped out by something else.

The survivors of the secessionist advance are dead, their suits cracked and sprouting fungal stalks. The Glare Drums, a mycelial network that has been growing in the flooded lower galleries for eighteen months, fires corrosive spore globules triggered by electromagnetic emissions. The network learns from squad sensor signatures, practicing its aim on empty corridors to refine its targeting. When the human squad activates full sensors to coor ...