Worm

These worms differ hugely in size, but every one is a long, tube-shaped burrower.

Purple worm: the dread of underground explorers, it tunnels through stone after anything it can feel moving, sensing faint vibrations 60 feet away. Reliable reports describe adults 8-9 feet thick and 140-150 feet long. A bite that hits with 4 or more to spare swallows the victim whole, provided it is no more than 8 feet tall and 6 broad. Within six rounds the swallowed creature is dead; within two hours it is digested, beyond any chance of being raised. Those inside can hack at the gut wall (AC 9), but the digestive fluids sap them, imposing a cumulative -1 on their damage. The tail stinger deals 2d4 and kills outright unless the victim saves vs. poison. Solitary except to mate, each hatchling digs away immediately and never meets its siblings again. The rock it swallows while tunneling is expelled back at its lair, and that waste includes gems and precious metals.

Mottled worm: an aquatic purple worm that lives in shallow bottom mud but often rises to hunt. It is otherwise identical.

Thunderherder: a desert purple worm only 3-5 feet thick and 5-10 feet long, with 7 Hit Dice, roving in herds of 10-100 a few feet beneath the sand. It eats small sand-dwellers and spews sand as it moves. Its mouth cannot hurt anyone, but a herd passing below shakes the ground like an earthquake.

Giant bloodworm: mottled green with a slimy dark brown belly. Hungry or trodden on, it latches on with its mouth for 1d8, then drains blood for 1d8 every round until killed or pulled free with a successful open doors roll. Fire deals it double damage, and even when it saves (at -2), it still takes full damage.

Bookworm: a gray library pest that changes color to blend with its surroundings, giving others -6 on surprise rolls. It cannot eat living things but chews through paper, bindings, leather and dead wood at 3 inches per round. When discovered it is quick to flee rather than fight.

Rot grub: a maggot that lives in garbage. Its chance of reaching bare skin equals the victim's AC, ignoring shields. It then burrows in, numbing the flesh with mild venom; each round the victim may attempt a Wisdom check to feel it. Fire applied to the infested area kills 2d10 grubs each time, but only during the first 1d6 rounds, after which they have burrowed beyond its reach. Cure disease destroys them. Left alone, they tunnel to the heart within 1d3 turns and kill the host.