Two entries with the name Dyonas.
As a youth, he befriended Diana, the Roman goddess of the hunt, who bestowed upon him a special gift: that his daughter would be loved by the most powerful magician in the world (Merlin). As an adult, he was strong and likable knight. He served the Duke of Burgundy, whose daughter (or niece) he married. As a present, the duke bestowed the forest of Briosque on Dyonas, and Viviane was born there.
He later served King Ban of Benoic – Lancelot’s father – and helped him in the struggle against Claudas. He also fought in some of Arthur’s battles against the Saxons, participating in their crushing defeat at the second battle of Clarence.
Vulgate Merlin | 1220-1235
Prose Merlin | Mid-15th century