I remember something about him being bastard-born. Something about how the Illyrians treated Azriel's mother. Although I'm not a 100% sure.

I know that he was treated like shit, but it says in Silver Flames that he hates Illyrians. I was just wondering if there was more to it.

@Dreaming Writer We still don't know everything about Azriel's story, and many believe that he might have a POV in future books so if there is more to it we will learn that later, so far that's what we know.

It's not all been revealed yet, but he was treated very poorly by them.