Demarax

The demarax resembles a crocodile studded with jewels, its dark hide set with tiny crystals of a hundred colors that grow thicker with age. It has a short, blunt face, a small mouth and three yellow eyes in a row across its brow. It plods so deliberately that folk of a lawful gate-town call a lazy worker a 'demarax walking uphill'.

Its only food is spell crystals, the magical forms that summoning and contact other plane spells cast on prime worlds take. It ignores all else; you could put a hand in its mouth unharmed. But anyone carrying a trapped crystal, or near one that appears, becomes an obstacle it will shove past single-mindedly.

Few creatures resist magic as well. A crystal touching it nearly always fizzles and is eaten, and feeding renews the rock-hard gems that give it a superb Armor Class. Other spells cast at it rarely work either. It senses crystals within 200 yards and can trick one into treating the demarax as its target, so the crystal swerves straight into its mouth. When its resistance fails, a demarax is sometimes summoned instead of what the wizard wanted, and simply stares around until it starves.

Provoked, it swings its tail, where the gems are heaviest and sharpest. Three times a day it can loose three magic missiles from its eyes, though this burns the energy keeping it alive and soon makes it hungry. Facing death, it can release a whirling storm of half-eaten crystals out to 20 feet; each creature there must save vs. paralyzation or be struck by one and suffer a random magical effect. The storm empties it, and unless it eats a crystal it starves in 1d6 hours.

Alone or in small groups, demaraxes wander the great planar roads looking for food. They speak a few halting phrases of the planar trade tongue, mostly about crystals and hunger. Each has perfect recall and cannot lie, repeating any conversation verbatim without necessarily understanding it, but past, present and future mean nothing to it, so questions must be very simple or it wanders off to forage.

Its hide carries (1d6+4) x 10 gems, 50 to 100 stones of 10 gp each. Its other crystals are too small to sell.

Its body turns spell energy into life and grants it a vast lifespan; some remember talks thousands of years old. Nothing can digest its crystalline flesh, so it has no natural predators, only gem hunters. A law-obsessed faction of sages claims the powers of law made demaraxes to curb the chaos of stray spell crystals, and by eating them they do prevent much mischief.