Krul is an undead warrior from a long-extinct culture. For reasons unknown to us he is cursed to eternal life, always remembering just enough of his past to cause pain at what he has lost. His emptiness drives him to search for a cure for his curse. All he wants is a way to die.
We know from his past is that he was raised pretty much as a Viking, sailing and plundering as his way of life. Even Krul himself only remembers flickers though, learning sailing tricks from his father, smelling a woman’s hair, and so on. His quest for release from his suffering leads him to fight and kill anything and everything, from minions to civilians to Daisy the Stormguard, who was revived as Alpha. His hope is that the Halcyon Well has enough….something…to break his curse, but if not he has resigned himself to forever wander the land, searching for death to claim him.