Though they vary widely in size, all the worms in this listing have some common characteristics. They are all burrowers with long, cylindrical shapes.

Purple Worm

A constant threat to subterranean explorers, the purple worm burrows through the earth in search of prey. The worm is sensitive to minute vibrations in the earth, and can sense prey at a range of 60 feet. Adult purple worms as large as 8-9 feet in diameter and 140-150 feet long have been reliably reported.

The worm attacks by biting; an attack roll that exceeds the required score to hit by 4 or more indicates the victim has been swallowed whole. This worm can devour creatures up to 8 feet tall and 6 feet wide. A swallowed creature dies in six rounds, is digested in two hours, and cannot be raised from the dead.

Anyone trapped inside a purple worm may attempt to cut their way out. The interior is AC 9, but digestive juices weaken the victim, causing a cumulative -1 penalty to the damage the victim can cause.

This worm has a stinger on its tail. Anyone hit by the stinger suffers 2d4 points of damage and must make a successful saving throw vs. poison or be slain instantly.

The purple worm is solitary and seeks a companion only to mate. The moment a new worm hatches, it burrows into the ground, never to be seen by its siblings again. As the worm tunnels, it consumes vast amounts of material that are excreted when it returns to its lair. Among the discharged substances are precious metals and gems.

The mottled worm is an aquatic variety of the purple worm. It inhabits shallow bottom muck, but it often surfaces to search for prey. Otherwise, it is the same as a purple worm.

The thunderherder is desert variety of the purple worm; they travel in herds of 10-100, several feet under the sands. They feed on small creatures in the sand, their bodies ejecting sand. They are 3-5 feet in diameter and 5-10 feet long, and have 7 Hit Dice. Their mouths are unable to cause damage, but their passage beneath an area causes an earthquake-like effect.

Giant Bloodworm

These worms are mottled green in color, with a dark, slimy, brown underbelly. A giant bloodworm attacks when hungry or when stepped on, by trying to fasten its mouth to its victim. If it hits, it causes 1d8 damage, and continues to cause 1d8 damage per round from blood drain, until killed or removed (removal requires a successful open doors roll).

These worms are especially vulnerable to fire, taking double normal damage from such attacks, or full damage when they make a successful saving throw despite a -2 penalty to the roll.

Bookworm

This worm can change its normal gray color to match its surroundings; opponents suffer a -6 to surprise rolls. Bookworms inhabit libraries, eating through the pages and bindings found there. They cannot eat living matter, but they will burrow through dead wood, leather, and other normal book materials at a rate of 3 inches per round. They are very fast and seek to avoid capture and combat when discovered.

Rot Grub

These maggot-like creatures live in refuse. If they touch exposed skin (they have a percentage chance to do this equal to the victim’s AC, not counting shield), they burrow into the flesh and secrete a mild poison that deadens the burrowing area; a victim must make a successful Wisdom check to notice the burrowing; one check is allowed each round. Fire kills 2d10 grubs per application to infested flesh, but after 1d6 rounds they are too deep to be burned. A cure disease will kill the rot grubs. If the worms are not stopped, they reach the heart in 1d3 turns, killing the victim.