Ugul’nst-vaer

A giant, demonic bat

Gargantuan

Ugul'nst-vaer was a monstrous bat that rose from the deepest parts of the underdark many years ago. No one quite knew what it was; the spawn of some primeval titan still imprisoned in the depths, the embodiment of some dark god set loose into the world, or some arcane mutation of what had once been a normal bat. Either way, those who heard its screech were unlikely to survive as it tore through settlement after settlement in the underdark, digging through the rubble after it attacked and gorging itself on the dead.

Eventually the drow of Alari were able to defeat it, brewing the most toxic poison the world had ever seen. They set up and waited, and when the creature attacked those that it murdered (and subsequently consumed) were loaded with vials of the poison. The creature died with that toxin flowing in its veins as it digested the dead, and once it lay rotting the drow began the process of preserving its body. Mostly this was meant as a trophy, a way to lord over other drow settlements that they had been the ones to defeat it, but also they hoped that someday, somehow, they could find a way to bring the creature back as an undead monstrosity under their control, something they could use to ravage cities on the surface in the way it had once killed so many of their own.

So far they have not been successful, but there is no telling when or if that might change.....