Azriel (pronounced: Ahz-re-el[2]) is an Illyrian and member of the Night Court. He is the spymaster shadowsinger of Rhysand and belongs to his Inner Circle. He is a childhood friend of Rhysand and Cassian.
He is considered to be one of the most powerful Illyrians in Prythian history, along with Rhysand and Cassian.
Azriel is the bastard son of an Illyrian lord. For eleven years he lived with his father, stepmother, and two older half-brothers. The two boys and their mother were cruel and spoiled. While living in his father's keep, his stepmother kept Azriel in a cell with no windows or light. He was allowed to come out only for an hour a day, and to see his mother for one hour every week. He was not allowed to train or fly, even when his Illyrian instincts urged him to do so.
When he was eight, his two cruel half-brothers decided it would be fun to see what happened when you mixed an Illyrian's quick healing gifts with oil and fire. They poured oil on his hands and lit them on fire. His father's warriors heard Azriel's screaming, and rescued him but not quick enough to save his hands, leaving them permanently scarred.
At the age of eleven, he was dumped in the Illyrian training camp, Windhaven, where he was well received by the camp lords due to his shadowsinging gifts. He eventually met Rhysand and Cassian, as they were training at the same camp. At this point, like Cassian, Rhysand's mother took him in, for she was a friend to Azriel's mother.
When Rhysand's father saw that his son had started to rival him in power and had allied with the two most powerful Illyrian warriors in history, he separated them in fear that they would eventually turn against him. Rhysand was given command over a legion, Azriel was kept as his personal shadowsinger, and Cassian was appointed as a foot soldier.
Once Rhysand became the High Lord of the Night Court, Azriel was appointed as spymaster and became part of his Inner Circle
(SOURCE: ACOTAR WIKI)