Kaeros was an Elder Breed dragon of the Order of the Flame, Bonded with Navaros. When Navaros turned against the Order, Kaeros apparently followed willingly. Upon founding the Dark Union and after recruiting other dragon riders to his cause, Navaros grew to resent sharing power with Kaeros. He used dark magic to absorb the dragons very soul and Kaeros' physical form was effectively melded together with his master.
When eventually Navaros' human body was destroyed and his soul flung into the Rift Gate, the soulless body of Kaeros went with him.
Kaeros returned 600 years later along with the newly resurrected Navaros. His former graceful appearance was no more. Now a great monstrosity, he was significantly larger and had grown four heads similar in appearance to a Hydra. This is possibly due to the corruption wrought upon his soul by Navaros. When Navaros' soul was banished from the body of Rynn's brother, Delon, he once again possessed Kaeros' body in an ill-fated, last-ditch attempt to kill the warrior woman and her bonded dragon, Arokh.
Drakan: Order of the Flame - Drakan: The Ancients' Gates