Simic

Simic was one of the Weavers, who lived thousands of years before the founding of the Seven Kingdoms. He resided in the underground city known as Greathome, where his magical and scientific research led to the creation of all manner of monstrosities and abominations. He is believed to have been crucial in the creation of the Tarrasque. He also experimented on modifying existing creatures, possibly becoming responsible for creatures like Owlbears, Perytons, Chimerae, and the like. He, along with the vast majority of the other Old Ones, perished in the unleashing of the Tarrasque.