Wraithworm

This big, powerful snake has coal-black scales, glowing green eyes and a diamond chain of deep purple bands down its spine. Its head is nearly as large as a man's and its fangs are three inches long. Bony spikes poke out along its back, never used in a fight, simply a warning to would-be predators.

Wraithworms haunt deserts, rocky wastes and badlands, and are especially common in the prison plane's sandstorm layer and a snowy, sandy layer of the plane of passion. Long soaking in planar energies has given these ordinary-seeming snakes strange powers.

Slow and lazy in movement, the wraithworm relies on stealth, then strikes with startling speed. Its bite deals 1d8 points of damage and drains 1d2 levels. Its venom acts slowly: over the next 1d6 hours it deals 3-12 points each hour, and its icy burn imposes -4 on the victim's attacks, saves and Armor Class meanwhile. The victim saves vs. spell to avoid the drain and vs. poison at -2 to avoid the venom.

The snake can take on wraithform, as the spell, for a turn out of every hour. While vaporous it slips through hairline cracks and is vulnerable only to +1 or better weapons, which makes it ideal for creeping up on meals or escaping enemies.

While solid, it may instead spend its whole action on a gaze that reaches 15 feet. A creature of 4 Hit Dice or less that meets it must save vs. spell or stand paralyzed for 2d4 rounds.

Cold and negative energy deal it half damage. Oddly, a priest who succeeds at turning as if facing a spectre holds the snake still for 1-3 rounds.

Solitary and fiercely territorial, a wraithworm drives every other predator from its range. It keeps no lair, spending its life prowling its territory for food.

Its abilities defy explanation. Level drain, cold resistance, an intangible form and frigid venom all suggest the undead. The favored theories say an evil power or great fiend made the species this way for its own ends or amusement, or that it simply lingered too long in the wrong places.

Even so, wraithworms are natural animals that fit their ecosystems without harming them. They eat small animals and birds and rarely hunt people; a human who gets bitten has usually wandered too near.