Antasillix was living like a normal green dragon when he was summoned by Tiamat. The goddess ordered him to find a cleric that was near the Pit of Many Colors, an abandoned bathhouse in the ruined city of Unthalass in Unther, and, after the cleric left the city, to attack and killed the cleric. Antasillix worked well and during the Rage of Dragons of 1373 DR, Tiamat summoned him to her lair in the Nine Hells. After the end of the Rage, he came back infused with infernal energies. He followed some wyverns but had only some bad encounters.