Phelpar

Phelpar was a mage of note from Rassatan in Samarach who lived some time before the 14 century DR.

History
Phelpar polymorphed his rival Selvar into a frog for several years. He used this opportunity to steal all of Selvar's spells and magic items and hid them in a secret cache in a tomb in the Rathgaunt Hills in the Shaar. Selvar was somehow able to transform himself back to his natural form and tracked Phelpar down to exact his revenge. He polymorphed Phelpar into a horse and rode him to death, then used his magic to speak with his corpse and learn the location of his magical cache so he could reclaim his stolen magic.