A frozen ocean moon circling a giant planet, sealed under a kilometres-thick ice shell that blocks nearly all sunlight. Tidal flexing keeps a dark, salty sea liquid beneath the ice, warmed and fed by mineral-rich vents on the seabed. Gravity is light and the cold water oxygen-poor, so life clings to the under-ice ceiling above and the vent fields far below.
Anchors in pale clusters around the seabed vents, feeding through bacteria housed in its gut.
You choose the situation, not the result. Selection acts on Brine Lashworm; the descendant appears above.
Climate
Resources & space
Predators & life
Habitat & extremes
Mate Brine Lashworm with another branch of the same lineage to make a hybrid.