Gargouille

Picture an ancient mosasaur, a long-jawed marine reptile from the age of great lizards, and you have the gargouille, a sea dragon counted among the worst terrors of the deep. It crawls slowly on land, yet coastal towns dread it.

In melee it either slaps with its tail for 2-20 or bites for 3-30. A bite roll of 19 or better swallows a victim of size L or less, who then takes 1-6 per round from stomach acid.

Its fame comes from its water breath. It conjures water inside its body and blasts it out as a 100-foot cone, 10 feet across at the mouth and 50 feet at the far end, for 5-50 points of damage (half with a save vs. breath weapon). A second save vs. breath weapon, at -2, is needed to stay standing for anything of size H or smaller. One round of this capsizes rafts, canoes, small sailboats and cogs, two straight rounds sink a full galleon, and two rounds on land flood an acre into ruin. Then it eats the drowned. Water attacks cannot harm it.

Like other dragons, gargouilles are loners, partly because even the richest waters cannot feed two. After brief mating, the pair part, and the female buries her eggs in an undersea cave or a remote shore so well that a party almost never finds them without the mining proficiency to spot the dig. Hatchlings emerge four months later able to fend for themselves. Gargouilles have no use for the treasure of the towns and ships they drown, but they keep both the loot and the wrecks as trophies to boast of their prowess, even to each other.

Fearless because always hungry, a gargouille eats anything alive, even dragon turtles, whales and giant whales when food is short, and krakens dare not trespass on its waters. It stays only where fish and prey abound, migrating and abandoning its lair when they run out. Rarely, several join breath attacks to cause great floods, whether to hunt or for some other reason.

Inside a slain gargouille is a sac as big as an elephant's stomach full of magical water. A vessel filled from it helps in crafting a decanter of endless water, an alchemy jug, a bowl commanding water elementals or a beaker of plentiful potions, and using it in any magical potion raises the base chance of success to 80%.