Much like Smidvarg, Darkvarg is an white Night Terror, with the exception of having red eyes instead of yellow, due to being albino. Unlike the other Night Terrors that live underground, Darkvarg has darker patches on his back.
Darkvarg and his fellow albino Night Terrors were discovered by Fishlegs Ingerman and Meatlug. Fishlegs was regarded as a leader by the Night Terrors. He named Darkvarg after Smidvarg due to their similar appearance. During that time, Darkvarg became exceptionally close to Fishlegs. When Fishlegs had to leave, the other Night Terrors attempted to stop him and wanted him to stay. However, Darkvarg, sensing Fishlegs' intentions, aided him and finally bid his farewell to Fishlegs.