Giant Nautilus

It looks like its small cousin grown huge. Native to elemental Water, it also swims certain upper-planar seas and, on the Prime Material, the deepest trenches. Telepathy lets it converse with any intelligent being.

Twenty tentacles ring its mouth, squeezing foes and pulling them to jaws that bite for 5d4 and swallow a man-sized victim whole on a natural 18 or better. It can split the tentacles among up to 20 targets or put them all on one, usually three per man-sized foe. A held victim has one arm pinned (01-50%), neither (51-75%), or both (76-100%), cannot cast, and hits the tentacle at -3 with one arm free or -1 with both. Only 15 points from an edged weapon severs a tentacle, never brute force, and it regrows in about a week.

It can pull a small ship under, or halt a larger one after a turn of wrapping and hauling. Six or more tentacles squeezing a hull for three straight rounds deal ramming damage and start it sinking.

It also has spell-like powers, using any one each round as it pleases: part water, detect magic, monster summoning I, II, and III, charm person or mammal, wall of coral (as wall of stone), lower water, detect evil/good, a 10-foot control temperature, and locate fish or plants. It can conjure a water elemental 3 times a day, and know alignment is always active.

A lairless loner, it lives 3,000-4,000 years and probably uses magic to go home to the Water plane to breed. On good terms with nearly all sea peoples, even sahuagin and the evil ray-folk of the deep, it often judges disputes for tritons, mermen, and locathah. Overfishing and pollution it halts by talk, then warning, then force.

Wrecks offend it, so it protects salvagers from deep predators. Indifferent to treasure but wise to greed, it makes them clear plain cargo wrecks before treasure ships, and haul up entire hulls, not just the goods.

It eats giant crabs, lobsters, and similar crustaceans, has no natural foes, and sometimes clashes with the kraken. Its shell is a rich prize: it can be fitted out as a roomy, almost crush-proof submarine.