Sourcrust

Overview

Sourcrust is a crust that grows on stone in the still, stale air of the deep: in sumps, closed galleries, and vent runs where the draught has failed. It is harmless to touch, but it does not grow where air moves, and so in the Stonewake Deeps a patch of it means bad air has been lying there long enough to grow something.

Appearance

It spreads over rock and old timber as a thin, wrinkled skin, pale sulphur-yellow to the colour of old cream, slightly damp and slick, with a crazed surface like dried paste. Thick patches build up into soft, pale ridges along the floor of a gallery, where heavy damps lie, or in the high corners of a roof, where the light foul airs gather. It gives off a sour smell like spoiled milk and wet iron, which the crust takes its name from and which hangs in the air around it.

Habitat and Range

It grows only where air has stood still for weeks: the low ends of galleries, sumps, closed side-workings, behind collapses, and in vent runs whose draught has failed. It is known through the inhabited and working levels of the Deeps and in the lowest workings of the Ironspine holds.

Behaviour and Temperament

It starts as faint yellow spots and spreads over a season. Once a draught returns it dries, cracks, and flakes away within days, and a patch that is drying is a patch the vent crew has done its work on.

Uses and Dangers

Its use is warning. Kobold crews, walking the vent rounds, chalk their warning mark beside every patch they find and report it, and Dwarven wardens read the chalk without needing to know the sign behind it. The danger is not the crust but the air it lives in, which can kill a crew that walks into it upright; the crust's sour smell is often the only smell bad air has.

Lore and Belief

Kobolds say the crust is the air going sour, as milk does, and that a crust found in a living gallery means someone has failed in their round. Dwarves sometimes say it grows on stone the mountain has stopped breathing through. Both treat the smell as a warning in itself, and a child who smells sour milk in a deep corridor is taught to turn around before looking.

Kobold crews still tell of the crew that broke into a sealed working full of sourcrust and old Dwarven gold, and the one Kobold who smelled the milk and dragged the others out before the air took them.

Where It Appears

• Overview: Plants and Fungi