King Derendil

King Derendil was Quaggoth who (rightfully so) believed himself to be a transformed elf prince. While travelling, he fell into a hole into the underdark, and slowly he and his servant Ahdice, became a Quaggoth during their time there. Derendil eventually overthrew the previous pack leader, and Derendil sought to take over the rest of the surface world with his newfound pack. He sent his pack out to the surface on several trips to collect prisoners so that he can interrogate them, thereby seeding parts of the underdark with overworlders.

King Derendil was killed by a group of adventurers during the 2nd Kraggenhammen Underdark Expedition.


Source: Out of the Abyss Pre-Made Adventure