Smoke Mephit

(from Planescape: Monstrous Compendium Appendix I - 1994):

Smoke mephits are crude and lazy. They spend most of their time sitting around invisible, smoking pipeweed, telling had jokes about their creators, and generally shirking their responsibilities. 

Combat: A smoke rnephit's two clawed hands cause 1d2 damage each. Its breath weapon consists of a sooty hall usable every other melee round, an unlimited number of times per day. This sooty hall automatically strikes one creature of the mephit's choice within 20’ (1d4 damage and blinded for 1-2 rounds), no saving throw. Smoke mephits can cast invisibility and dancing lights once each per day. 

Once per hour, they can attempt to gate in 1-2 other mephits, fire, magma, smoke, or steam. If two rnephits arrive, they are the same type. 

Contact with any kind of smoke lets a smoke rnephit regenerate 1 hp per turn. When a smoke mephit dies, it disappears in a flash of flame. This flash causes 1 hp damage to all creatures within 10’ 

Ecology: Lower-planar beings traditionally dispatch a smoke mephit as a gift to enemies, a gesture of insolence and contempt that amounts to a declaration of vendetta.

(from Planescape: Monstrous Compendium Appendix III - 1998):

The ecology of the Paraelemental Plane of Smoke is quite involved, even though it doesn't have many inhabitants. The plane is "ruled" by a smoke mephit named Ehkahk, but most look upon him as nothing but a joke. Efreet and djinn often come to the plane (particularly to wage wars against each other), and they pay Ehkahk no heed whatsoever.

Smoke paraelementals also ignore the so-called lord of the smoke mephits, choosing instead to form their own kingdoms and follow their own nobility. One thing that's sure to confuse a planewalker is the fact that the mephits have their own rulers and realms and the paraelementals have theirs - and the borders (which are difficult to ascertain anyway) don't coincide. A crutter travelling through the kingdom of a smoke mephit count might pass through three other realms belonging to the smoke paraelementals. But the paraelementals don't care; they rarely interact with other denizens at all. They have taken it upon themselves, however, to rid the plane of meddling outsiders like the efreet and djinn.

The predatory belkers hate the efreet as well. Belkers attack the native mephits and anything else that wanders into their path, but they truly despite the fiery genies, who try to conscript them as soldiers in their endless little wars. Fact is, the recruitment strategy's backfired on the efreet, for now if the belkers must choose sides, they choose the djinn.

Creatures known on some prime-material worlds as vapor rats also dwell on Smoke, often serving as pets for self-proclaimed mephit nnobles. And everything on the plane simply avoids the lumbering creatures known as sootbeasts.