In the flooded pump galleries beneath Blackwater Vault Seven, failing machinery is driving corrosive water higher while the Silica Maw spreads through the walls, doors, and abandoned filtration chambers. Expeditionary Containment Unit 12 descends Pump Shaft Seven to extract Lieutenant Aldric Senn and contain the organism before it compromises the fleet’s genetic archive.

The soldiers clip into a single descent line, force their way through trichome-choked corridors, and fire solid slugs at heat-tracking symbionts. But the Maw breaches their armor, infects exposed tissue, and has fused the still-conscious Senn into its colony while stealing memories and defense codes directly from his mind.

This is "The Breathing Shaft" by Sascha Schmidt