Imp

A dark red, 2-foot humanoid with leathery bat wings, a barbed tail and gleaming white horns and teeth, the imp can also polymorph into two animal forms, usually a raven, goat, giant rat or large spider, identical to the real beast.

Its tail stinger deals 1-4 and injects poison so strong that a failed save vs. poison kills instantly. In animal form it uses that animal's attacks, though goat and raven forms deal no damage.

In any form it can use detect magic, detect good and invisibility at will and suggestion once daily. It is immune to fire, cold and electricity, saves against other spells as a 7 HD creature, is harmed only by silver or magic weapons, and regenerates 1 hit point per round.

Sent from the darkest evil planes to spread wickedness, imps assist lawful evil wizards and priests, answering find familiar when a caster seems worthy. The imp immediately begins steering its 'master', keeping up the pretense of obedience while using him the way a craftsman uses a tool. Ambitious in their own right, imps loot their victims and pilfer valuables.

Slaying its body on the Prime merely sends its spirit home to be remade and, in time, returned.

Within a mile the pair share telepathy: the master perceives through the imp's senses, infravision too, gains its 25% magic resistance and regeneration, and acts one level higher. Beyond a mile he acts one level lower. Should the imp die, its master drops four levels at once, regained normally.

They run errands for the lords of the dark planes, but their true task is spreading evil among mortals.

The quasit is the chaotic evil counterpart, granting its chaotic evil wizard or priest the same benefits and drawbacks. Its two alternate forms are usually chosen from wolf, frog, bat and giant centipede, and its magic works in each.

It claws twice for 1-2 and bites for 1-4; each claw hit forces a save vs. poison or the victim's Dexterity falls by 1 for 2d6 rounds, cumulative with further wounds. It uses invisibility, detect magic and detect good at will, a 30-foot fear blast once daily, and commune once weekly to question the lower planes up to six times. It regenerates 1 hp per round, takes harm only from magic or cold-iron weapons, has 25% magic resistance, saves as 7 HD, and ignores fire, cold and lightning.