Cynis: The Southreach Saga
Tellevar is an adult black dragon who lived near the Saltmarsh. He is the only know living son of The Lady of the Marsh.
After the heroes destroyed the dragonborn vampires, Tellevar told them that they had freed him from his mother's curse. But as neither he nor they were ready to fight The Lady of the Marsh, he left saying that he would return when the time is right.