Harley is 6ft2in in his human form and over 8ft in his demon form. He has shaggy auburn hair and amber/yellow eyes. He always feels warm to the touch. He has a flame tattoo sleeve on his right arm in human form with a horned skull on his shoulder and a dragon on his forearm. He typically wears tank tops, biker jackets, jeans, and boots. He drives either a pick-up truck or a motorbike. He speaks with a Texan accent. He currently works as the owner of a strip club and will often take to the stage himself. The club also operates as a hidden brothel and he's more than willing to be a service top or bottom if his staff need a break from certain clients.

He used to be a demon known as Valka, and was of fairly high status thanks to his father being the Lord of Fire on the council. He held the position of Fire General for a long time before eventually defecting when he discovered his father was working alongside the Lord of Chaos in the first Chaos War. Due to policical meddling, he was banished from the demon world, labelled as a traitor by his father, and left all of his demon life behind to live in the human world.

Harley can summarise his life in various losses. First was the loss of his mother when his father pulled him away from her to raise him as a perfect solider. Second was the loss of his soul-bonded partner who died at the hands of his father during the rebellion Harley lead against him. Third was the loss of his brother when Harley couldn't bring himself to kill him when he was used against him, also during the rebellion. Then was the loss of his close companion, a demon hunter named Chase, who was the first person to show him how to live as a human, who tragically died during a hunting job when a rogue demon got a lucky shot. He's never allowed himself to grieve for any of it and thus holds a lot of negative emotion on his shoulders which he hides behind a charming and flirtatious personality. For a long while it stopped him getting truly close to anyone, afraid of losing them too.