Ourobouros

Ourobouros Stalks-By-Night was a legendary Elyos daeva with unknown heritage and about two hundred years of lore. He was not associated with any great House or legion, so he was wondering as he pleased. Even though he was loyal to Ariel, he didn't miss a chance to piss her off, and often did nasty things simply because he could. He is known to have infiltrated Asphel's palace and killed his spymaster on his own. The truth of this story is that he had an Asmodian lover - Daiyu, whom he wanted to take with him in Elysea and hide under the noses of Elyos nobility. The night he snuck into the palace to steal her away the unfortunate spymaster stood in his way. Ourobouros succeeded in his plan, he brought Daiyu with him, presumably with the help of the illusion enchantment and lived with her. They had one son, whom they named Ourobouros as well, but called Oros as a short usename.

At some point Ourobouros defeated a Balaur prince in a one-on-one battle and took his sword for his own - a dark blade called The Last Word. This victory is depicted in a painting that hangs in the library of Sanctum, with a writing on it: "Ourobouros Has The Last Word".

Presumably some time after losing Daiyu (by all appearances, she died) he died. It is unclear what happened to Ourobouros Stalks-by-Night. Taion tells Jaya he's been dead for about twenty years. He also says "Suffice  to say that Ourobouros did not fall in a way that my exalted aunt believed worthy of his station, or his legend". Ariel, feeling his demise might seem like a display of weakness, forced his son, who shared twin-like similarity with him and was a daeva and a skilled warrior in his own right, to play the role of his own father.

Trivia
* Ourobouros the name comes from a symbol used in alchemy and philosophy: a dragon holding its tail in its mouth. It symbolizes the endless cycle, where the end is a new beginning. It is quite similar to the life cycle of Phoenix.