Once a friendly dragon that worked alongside an uncorrupted King Lysandre and Reihan, he had a dragonborn form and was not always host to an incarnate within him. He was king of the Dragon Empire, which owned all of Alderwyl before they allowed some space for mortals to make their homes.
The people of Alderwyl attribute the Rage of Dragons to Lusacan’s influence somehow.
After he was freed by Nagasha using Rose, he flew west.
Lusacan was the strongest incarnate and the first to be imprisoned (not entirely true)? He could drink light, and is the most difficult to contain. He can swallow the light of Lithiel’s wish because Oris got her power from the Luminos as well.