Phobos who is often referred to as Achilles is the grandson of the great Achilles of Trojan War fame. He was the son of Neoptolemus (Achilles's son who also fought in the Trojan War) and Hector's wife Andromache who was Neoptolemus's concubine after he took her as a prize from Troy. 

His name in Greek means "fear" and he was every bit as frightening on the battlefield as his father and grandfather before him. It was said no man could ever slay Phobos and so it wasn't a man.

It was a woman bent on revenge. Using Phobos, she gained access to his brother's palace and when Phobos tried to stop her, she stabbed him through his heart, then killed every living member of his family. 

As a result, he has vowed to never trust another woman again. He keeps to himself and is a bane to all Daimon born.