Ildriss

(From Planescape: Monstrous Compnedium Appendix II - 1994):

The ildriss, or wind terror, is a grue from the Elemental Plane of Air. On other planes an air grue is either invisible or seen as a fog-like cloud with vaporous tentacles and three faintly gleaming red eyes. The latter is its natural form on its own plane, where it is generally gray, pale yellow, or (rarely) white. Eyes are pyramidal, ranging from dark orange through scarlet to maroon. 

Combat: The ildriss can move invisibly on the ground or high up, so opponents’ surprise rolls take a -3 penalty. The air grue attacks first in any round. It whisks about in the former guise, but to attack it must become more substantial. It forms as an entity of swirling mist, its fog arms shooting small particles. These strike like a sandblast (3d4 damage). 

Their nebulous form makes air grues hard to hit (AC 2). They are immune to weapons of less than +2 enchantment and to air-based spells such as lightning bolt, cloudkill, stinking cloud, cone of cold, invisible stalker, and wall of fog. The presence of an air grue dispels all such magic within 50’. even permanent effects. Magical items are unaffected.

Habitat/Society: Ildriss form ever-shifting cliques within semi-stable tribes. They follow no chain of command; those with goals lead the rest in temporary alliances. They do not betray each other, though they may not cooperate. Most are servants or spies of Yan-C-Bin, an Elemental Prince of Evil.

Ecology: Outcasts on the Elemental Plane of Air, air grues are parasites and (hesitant) predators. They eat clouds, birds, and small creatures of elemental air. During mating season they defend their territories against interlopers; these territor are drifting bodies of cold dry air

(From Complete Arcane - 2004):

Some unseen force seems to hover in the surrounding air. Wild winds whip past, carrying dust, debris, and litter in their wake.

An ildriss, or air grue, is the product of an evil spell corrupting the substance of elemental air, It is a capricious and violent creature that rages constantly against its surroundings, trying its strength against any obstacle in its path or hurling items through the air from sheer spite. It most enjoys venting its anger against any Material Plane creature it encounters. 

An air grue is normally invisible, but invisible, but if rendered visible, it appears as a roiling cloud of dark vapor, its face marked by angry, changing features. It speaks Auran, but it is more prone to simply scream in inchoate anger than attempt to communicate. An air grue is about 4 feet in diameter and weighs 10 pounds.

To determine the type of spell object contained in an air grue, roll d%: 01-70, invisibility; 71-100, fly.

Combat: An ildriss uses its speed, maneuverability, and invisibility to best advantage in combat. Air grues like to race through an enemy's ranks, striking foes at random to cause the most mayhem and uncertainty. 

Invisible (Su): Air grues are naturally invisible, gaining total concealment.