Srossar was an ancient dragon. Around 1240 DR, some agents of Tyranthraxus (who were in turn deceived) tricked Srossar into believing that bathing in the Pool of Radiance, a portal to an unknown dark plane underneath Valjevo Castle, would give him greater wisdom and understanding of the metaphysics of the universe.
However, in truth, when the dragon entered the pool, Srossar was possessed by Tyranthraxus. Tyranthraxus immediately commenced building an army of monsters for the subjugation of Faerûn.
- Pool of Radiance (unnamed)