Afanc

This huge fish is feared for the whirlpools it spins. Seamless gray to blue-gray scales and sheer bulk lead most sailors to take it for a whale on first sight, until its vertical tail fin and wide-mouthed, plainly gilled head show it to be a fish. The creature has some wit: sea tales tell of afanc that picked up human speech, even songs, delivered in a booming, gravelly voice and used to steer crews toward disaster.

The afanc rarely hunts, preferring to eat whoever comes hunting it. It cruises slowly on the surface of shallow seas, hoping to pass as a whale. When a vessel 30 to 60 feet long approaches, it begins circling at its normal speed 100 feet out, close to the surface; the water's partial cover gives missile attacks against it -2, plus range penalties. Anyone who closes to melee draws it off the ship to eat them instead.

Making the whirlpool takes 1d4+4 rounds. Each round it closes to 40 feet, swims faster and dives deeper, the ship spins harder, and missile penalties worsen by a further -2 each round, bottoming out at -12. Once it is swimming at movement 30, the rushing current and the fish's inborn magic suck the vessel down, taking a number of rounds equal to the ship's length divided by 10 feet. That magic is why casting dispel magic on the fish, or having magic resistance protect the vessel, halves the rate, so sinking takes a round for each 5 feet of length instead.

Ships longer than 60 feet are usually ignored but may be rammed; rafts and boats shorter than 30 feet nearly always get rammed in an effort to overturn them. Treat a ship as AC 5 (AC 3 while taking evasive action), improved at the DM's option by unusual materials or magic. Beating the required attack roll by at least 4 overturns the craft. Any ship that is rammed rolls a save vs. crushing blow, going down within 1d10 rounds on a failure; typical hulls use the thin wood column, so they need 13 or more.

Survivors in the water face two front flippers (3d4 each) and a bite (5d4). A bite that beats the needed roll by 4 or more swallows a Large or smaller creature whole; death comes after six rounds and full digestion after two hours. A swallowed victim can try to cut free against an interior of AC 8, but digestive juices impose a cumulative -1 per round on the damage it can deal.

Though a saltwater creature, the afanc swims up the mouths of large rivers to spawn. Many creatures, humans among them, prize its eggs as a delicacy.

It has few natural enemies, but humans turn its bones and scales into weapons and ornaments.

Rivers sometimes hold packs of 3d6 young afanc, none longer than 15 feet. Each has 5 HD, 1d4 flippers and a 3d4 bite, and six or more of them together can churn up a whirlpool as an adult does.