Tekthyrios

Tekthyrios was a storm dragon living in a temple on Celestia.

History
A portal was located in Tekthyrios's belly that was connected to the inside of a giant snake in the City of Brass in the Elemental Plane of Fire. A priest of Cyric named Zasian Menz and the cambion Kaanyr Vhok used this portal to enter Celestia from the City of Brass; Kaanyr escaped from within Tekthyrios by means of purgative mushrooms delivered by the alu-fiend Aliisza, though in the journey they lost 12 years. Zasian instead possessed the dragon, as was his plan all along. The draconic hobgoblin Myshik Morueme followed Zasian and Vhok and, once emerging from the dragon's maw, swore to serve the storm dragon, having no awareness of Zasian's possession.

Though Tekthyrios fought Zasian for control, the priest was easily able to keep him at bay while using the dragon's body to wreak havoc on Celestia. Once Tekthyrios was no longer useful, Zasian forced the storm dragon to impale himself on a broken tree and returned to his own body. Zasian emerged from the dragon's gullet as Tekthyrios died, swearing revenge on the priest with his last breath.

Novels

 * The Gossamer Plain (unnamed)
 * The Fractured Sky