Bookworm

Bookworms are tiny, about an inch long, and normally a drab gray, but like chameleons they automatically take on the colors of whatever they rest on. Their good Armor Class comes from quickness; one caught sitting still is only AC 9. Wizards dread them, since they can smell scrolls, maps, tomes and spell books up to 60 feet away.

Thanks to its camouflage a bookworm imposes -7 on adventurers' surprise rolls, reduced to -4 against someone who can see invisible things. Because it is so small, fast for its size and harmless-seeming, even normally hard-to-surprise characters such as rangers and monks suffer these penalties. After gaining surprise, there is a 25% chance it is spotted clinging to a leg or pack; otherwise only its loud chewing betrays it, with a base 50% chance per round that the carrier hears it. A feeding worm stays still until attacked, then flees if it can, leaping 10 feet and racing back to its lair.

Living tissue is indigestible to it, but it tunnels 3 inches per round into dead wood or leather and needs only one segment to get inside a leather pack or scroll case. Scrolls and spell books disappear at one spell level per round, so a scroll holding one 5th-level spell lasts five rounds.

Lairs are always libraries or storerooms, active or long abandoned. There is a 30% chance some paper has survived: a map (60%), a scroll (30%) or an arcane book of wizard level 1-8 (10%). Any spell books found should suit the party's level, but 1d10-1 tenths of each (0-90%) has been eaten.

A mating pair produces 80 eggs, roughly half hatching a month later. The pure white larvae die within an hour unless they find paper, and they gain their gray color from the ink they eat. That same ink slowly poisons them, so they live only two or three years, and they die after their single breeding. Careless adventurers who blunder into a fresh brood can do enormous harm by carrying larvae along; a few hidden in a pack on a city street can spread to the libraries of sages, temples, wizards and governments.

A bookworm always heads for the biggest store of paper nearby. Its diet makes it valuable to alchemists, chiefly for the ink used to scribe protection from magic scrolls; the leftover ink in its body is what matters, so darker worms are better. A bookworm can also serve as a weapon, wreaking lasting revenge when set loose in a wizard's tower, and a few prisoners have walked free after key evidence vanished during their trials. The tactic is tricky, as captive worms are hard to keep alive, and risky, since a released worm may follow its handler home.