BOZ, Im not sure if you're also looking for Birthright's old awnsheighlien, since they're somewhat setting specific, but they are unique beings with power thats divine in origin. Most of them can be found in the old "Blood Enemies: Abominations fo Cerilia" book, but there's one thats elsewhere:

Planes of Conflict mentioned an awnsheigh called only the Blowfish that lived on Gehenna. A humanoid figure with short black spines all over its body, the Blowfish is strengthened by the poison gas in its layer, and it hunts the occassional proxy to drain it of its divine essence and grow stronger.

On some other notes...one of the last 2E Dragon issues had six unique dragons, children of Tiamat and Bahamut.

Planescape added quite a few Abyssal Lords that never got statted. I can't remember them all, but one that stuck in my my head: Pale Night, the mother of Graz'zt (and several other lords). Sorry I can't be more help here.

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