Piercer

A piercer is a gastropod whose shell grows into the shape of a cave stalactite, and without that shell it would resemble a long-tailed slug. Clinging to the ceiling, it is virtually identical to the real limestone formations around it. Only careful close inspection reveals the two tiny eyestalks curled against its side. They come in four sizes: 1 foot (1 Hit Die), 3 feet (2 HD), 4.5 feet (3 HD) and 6 feet (4 HD).

Piercers sense sound and body heat, a person's included, up to 120 yards away. When noise or light stays in one place for many minutes, they creep slowly across the ceiling until positioned above it. Then they let go and impale the target with the point of the shell.

Because they blend so perfectly with natural rock, a party suffers a -7 penalty on surprise rolls against them, so they are surprised unless something improves the odds. Each piercer gets a single strike. If it fails to kill, it must crawl back up a wall to its perch before trying again. On the floor it is slow and easy to finish off, though its soft underside sweats a corrosive acid when exposed to air, dealing 1 point of damage to any flesh it touches, which usually discourages natural predators.

These mindless mollusks live in caverns in clusters of roughly ten, preferring spots above busy paths, so they gather near cave mouths. Outside of mating they keep to themselves, but each colony senses its members, and they often fall together to share the kills, turning a quiet passage deadly in an instant. Stories speak of vast caves far below the surface with hundreds of piercers. They care nothing for treasure, only for food.

A parent lays clutches of six to eight eggs, each the size of a hen's egg, in quiet corners of the cave. Hatchlings are fungus-eating slugs. A few months later they crawl up the walls, ooze a substance that hardens into the stalactite shell and start waiting. A piercer lives four years and gains 1 Hit Die each year, so a colony holds roughly equal numbers of each size: twelve piercers would be three of each.

They can fast for months. A second stomach keeps food from spoiling, and alchemists hunt piercers to refine a substance from this organ that preserves food and rare ingredients for weeks. They also keep a reserve of water drained from prey, good for months. They taste like snail with a bitter finish, and their eggs and young are not sold on the open market.