Sean Dolan was the squire of Dane Whitman, who entrusted him with the Ebony Blade when he decided he would rather wield the photon sword than deal with the EB's blood curse.
But sadly, Sean didn't have the willpower to resist the blade, and once he unsheathed it, he transformed into the Bloodwraith. A bloodlusted killer and consumer of souls. He grew so powerful after killing an entire country and absorbing their souls that the Avenger's couldn't stop him, but only trap him for eternity via Wanda's magic. Strengthening the bond between him, and the souls of Slorenia's people which he sucked into his sword.