Coral

Coral is the hard, calcium skeleton built by soft polyps that cling to the seabed and sift food from the water with clusters of tiny tentacles. The stony branches protect them, giving each polyp a shell to pull back into when danger nears. Reefs grow mostly in tropical waters along coasts, around islands, and over submerged volcanoes. Common coral is a minor hazard for the cautious: its cuts draw aggressive predators, a few kinds are poisonous, and reefs wreck ships that run onto them.

Named for its folded, ridged surface, brain coral is yellow, brown, or olive and bleaches bone white out of water. Like plainer kinds it grows in warm tidal waters as deep as 1,000 feet, usually on reefs or atolls where food is plentiful.

Its skeleton is AC 5 and must absorb damage equal to the polyp's full hit points before it cracks enough to expose the AC 10 polyp within. Slashing and piercing weapons do only half damage. Stinging cells across the skeleton attack any flesh that touches it, injecting a mild neurotoxin: a failed save vs. poison (at +4) leaves the victim paralyzed 1d10 rounds.

Each colony is psionic, with ego whip and id insinuation for attack and mind blank and thought shield for defense. It has at least two of these telepathic powers: domination, mind link (animal telepathy only), contact, ESP, and invisibility, possibly along with the psychometabolic devotion cell adjustment. There is a 25% chance it also has psychokinesis, namely telekinesis and ballistic attack. With telekinesis, a threatened colony can push attackers away, or batter a single foe with flung seabed debris (ballistic attack) for 1d6 each round. One with ESP may probe visitors' thoughts.

Its tube, 2 to 8 feet wide and 2 to 20 feet tall, looks like valuable coral in white, pink, or red-orange. The worm inside is a long, black, sluglike body that exactly fills the tube.

When prey nears the reef, worms shoot out to full length and bite with mouths lined in coarse bony plates that can grind coral and chew through armor or a ship's hull. Bite damage scales with size at 1d4 for each Hit Die (4d4 for a 4 HD worm). Threatened, a worm withdraws into its tube, where only a stubborn predator can reach it. The tube's exterior bristles with razor ridges several feet long and up to half a foot tall (4-6 inches) that slice anyone who brushes them for 1d10, while the inside is smooth as pearl.

Safe in its tube a worm is AC 0. It may leave to chase swimmers or boats, but out in the open it is sluggish (MV 3) and drops to AC 8. They attack most creatures, though certain eels and lampreys share their reefs and eat their leftovers. The tubes are worthless for trade but make prized homes for many sea creatures once the worm has moved out.