Quasit
From Ardrana
Quasits are chaotic evil counterparts to imps. The chaotic evil priests and wizards which quasits "serve" gain the same benefits and disadvantages that an imp's master does. The average quasit is a two foot tall humanoid with leathery, bat-like wings and sharp, twisted horns. Its skin is a dark red and its horns and jagged teeth are a gleaming white. The quasit lacks the barbed tail of the imp.
Quasits are beings of a very evil nature who originate on the darkest of evil planes. They are the errand boys of the powerful evil beings who command the darkest planes. They often act as emissaries and agents, but their primary task is to enhance the spread of evil on the Prime Material Plane is to spread evil by assisting chaotic evil wizards and priests. When such a person is judged worthy of a quasit's service, the quasit comes in answer to a find familiar spell.
Like imps, each quasit can assume two other forms. Those most commonly chosen by quasits are bats, giant centipedes, frogs, or wolves. In such forms quasits are physically identical to a normal animal.
The quasit attacks with its clawed hands and its deadly bite. The quasit's claws are coated in a toxin which causes anyone struck by them to lose their dexterity. They regenerate, and can unleash a blast of fear with a 30-foot radius once per day. Quasits can only be harmed by cold iron or magical weapons. They are able to resist magic to some degree.
Once they have contacted their new "master", quasits begin at once to take control of his actions. Although quasits maintain the illusion that the summoner is in charge, the actual relationship is closer to that of a workman (the quasit) and his tools (the master).
Although a quasit's body can be destroyed on the Prime Material Plane, it is not so easily slain. When its physical form is lost, its corrupt spirit instantly returns to its home plane where it is reformed and, after a time, returned to our world to resume its work.
While they are technically in the service of their master, quasits retain a basic independence and ambition to become more powerful someday. They may acquire treasure from those they slay, and will often pilfer valuables encountered during their travels.
The quasit confers some of its powers upon its master. A telepathic link connects the two whenever they are within one mile of each other. This enables the master to receive all of the quasit's sensory impressions, including its 60-foot infravision. The master also gains the quasit's inherent magical resistance and is able to regenerate just as the quasit does. If the quasit is within telepathic range, the master acts as if he were more powerful than he actually is. Conversely, if the quasit is more than a mile away, the master acts as if he were less powerful. If the quasit is killed, the master's power instantly drops significantly.
Quasits are common in The Abyss. They are formed from larvae by powerful fiends. Quasits do not age naturally and are remarkably durable. Speculation, fostered by the quasits themselves, has it that fiends evolved from quasits.
Note: Quasits originally appeared in this form in the 2nd Edition Monstrous Manual for the AD&D game from TSR. Their use here is for the purposes of providing context for the campaign only.