Quelzarn

Built like a monstrous eel, a quelzarn runs thirty to forty feet from snout to tail, its slick hide mottled green or brown. That coating of slime lets it breathe air through its skin and often hosts clinging weeds and moss. A spiny fin runs the full length of its back, broad leaf-shaped flaps shield the gills behind its wide, fanged jaws, and a bony crest like a fin tops its head. Its eyes look strangely human, and together with its long body and interest in magic this leads some to mistake it for a naga.

A quelzarn eats anything alive, and carrion when food runs short, spending its days either hunting or lying still to digest. Once per turn it can cast hold monster at a range of sixty feet, both in fights and to pin prey; a favorite trick is freezing a sailor on a dock and then surging from the water to snatch him away.

Its bite deals 3d4 damage, and it can swallow whole any creature up to 4 1/2 feet tall, though even a held victim gets a Dexterity check to avoid being gulped. Inside, a victim takes only 1d2 from the teeth but drowns after six rounds. The gullet is AC 9, and dealing 20 damage from within makes the serpent spit out whatever it holds. An enraged quelzarn may cough up a meal deliberately just to bite it again.

It has natural magic resistance and total immunity to electricity, natural or magical. Spells that would dominate its will attract it, and every second round it gets a save to break free of such control, whether from a spell, an item, or a spell-like power. Foul water from crowded harbors or vast swamps hardly bothers it.

These serpents inhabit both salt water and fresh, swimming far over their lifetimes, and seem to mate only rarely, in deep caves beneath the sea. They may help other creatures in exchange for food and never attack their own kind. Two that find the same prey simply ignore each other and attack separately, neither sharing nor squabbling.

Their origin is probably magical, perhaps from experiments by wizards of an ancient southern empire, where they were once hunted for sport.

Quelzarn keep no lair. Treasure near one consists of swallowed inorganic items such as coins and gems, since its digestive juices slowly dissolve flesh and even bone. Brain matter and cranial fluid make good spell ink for slow and hold magic and can be distilled for crafting rings of free action, and its tissue can stand in for other ingredients when seasoning wood for wands of lightning. The leathery skin stops making slime once removed or once the creature dies, and soon withers into nothing useful.

Greater quelzarn, larger and very rare if not extinct, appear in old hunting chronicles of that same empire. They possessed spell turning like the ring of that name, were cunning and highly intelligent, often lured hunting vessels into ambushes, and sometimes allied with other sea creatures.