Betewl the Beholder

Betewl the Beholder was one of the Triumvirate ruling the Dragon Army of Tiamat along with Llolth , Queen of Spiders, and their ultimate ruler, Kodarek the Dread.
After the Dragon Army's defeat, Llolth returned to the Underdark and Kodarek the Dread was killed by The Dragon Watch.  Betewl retreated with the remains of the Dragon Army to the Dragon Temple in Sundra where he still rules to this day.