Ardleon

Ardleon is/was an angel of the High Heavens.

Biography
Ardleon fought beside Tyrael in a battle of the Great Conflict. He was forced to call for aid, and Tyrael, despite being poised to deliver a killing blow to Azmodan, came to his comrade's side.

The event would haunt Tyrael's memory even thousands of years later, reflecting that if he had struck Azmodan down back then, the Lord of Sin would have never brought his forces to Sanctuary. However, The Nephalem held no judgement.