Diluc Ragnvindr is a rich wine tycoon of Mondstadt, owner of Angel's Share. He was a famed knight of Favonius alongside his adopted brother Kaeya, but left after his father Crepus's murder was covered up by the Knights.

Now, he secretly takes the alias of the Darknight Hero at night, hunting down criminals as a vigilante. He hates all the knights including Kaeya, as they let his father die. 

He is nonchalant and cordial, if a bit aloof. He fights brutally, using a claymore and a Pyro Vision.