Giant Clam

Giant clams, a group that also covers giant oysters, scallops and their kin, live in shallow seas no deeper than 200 feet. The soft animal shelters inside a heavy shell that it opens to feed and slams shut against danger. The upper shell is light brown, sometimes marked with white, and the lower one white. Tiny blue eyespots along the shell's rim tell light from shadow and notice movement but cannot judge size, and organs near the front of the hollow that cradles its soft body sample the water for chemical traces. Any communication with one would have to be empathic, and only at the most basic level.

A giant clam does not hunt anyone, but it can be deadly to the careless. If threatened, or if something reaches inside, it clamps shut. Its adductor muscles, which work the hinge, are so strong that prying the shell open again requires a successful bend bars roll. Some species have sharp, wavy-edged shells that sever a trapped limb on a natural 19 or 20.

Clams are seldom found in large numbers, though tales of vast beds persist. A clam is not rooted in place: when food runs low it moves across the seabed by pumping water through its siphons. It strains small shrimp and other tiny animals from the water and also lives off algae growing inside its mantle. Its outer cilia have become tentacles about 2 feet long that pass food to its stomach, too feeble to harm or hold anything with Strength above 6.

Some sea peoples, tritons among them, farm beds of domestic giant clams or oysters. Their chief predators are giant starfish and, naturally, greedy humans. Mother-of-pearl coats the inside of the shell, worth a base 50 gp and as much as 500 gp, determined with the standard gem tables. One giant clam in twenty (5%) holds a single great pearl valued at 500-1,000 gp by size and quality; it might be as big as a fist but is duller than smaller pearls from ordinary oysters. Giant oysters have a 25% pearl chance, and their base values are doubled. Clams collect no treasure on purpose, but 5% of the time coins, gear or minor magic from some drowned victim lie scattered or buried in the silt around one.

Bigger or smaller specimens can be made by giving them 1+1 Hit Dice per two feet of shell width and adjusting the rest to match. Unproven rumors speak of colonies of intelligent, even psionic, clams and oysters.

To an untrained eye this scallop looks just like a giant clam, but it is a bit smarter and actively hunts. It swims by flapping its shell like a butterfly's wings, and by blasting out water it can jet backward to ram a foe within 30 feet for 1d10 damage.

Its usual attack is a puff of mild nerve toxin from its exhalent siphon, spreading into a cloud 10 feet across. Anyone in it who fails a save vs. poison is paralyzed for 1d12 rounds. The scallop then seizes the helpless prey with its cilia and either pulls it straight into its stomach, where digestion deals 1 point of damage per round, or saws it into smaller pieces with its shell edges for 1d3 per round. Sometimes it buries itself in sand to hide from predators or ambush prey, and while concealed it imposes -5 on opponents' surprise rolls.