"Perhaps you have heard the accounts of my son's horrible death at the hands of Baal's minions. He was my last living child... The oath of compassion I have taken as a healer extends only to humankind. Cut them down, warrior. All of them!"— Malah, stirred to rage and grief over Bannuk's death(src)
Bannuk was friends with another Barbarian who headed south after news of Diablo's re-emergence in Tristram reached the northmen. The Barbarian and Bannuk did not part on good terms, as he could not understand the wanderlust his friend possessed. As Bannuk grew older however, he began to experience the same desire.
Two years after his friend's departure, the Barbarians were faced with their greatest challenge—an army of demons led by Baal, Lord of Destruction. The army encircled Harrogath and lay siege to it. While leading a successful campaign against Baal's forces, Bannuk was impaled on a demon's spear. His wound was so severe that even Malah admitted that quick death was a blessing. Qual-Kehk, who regarded Bannuk as the defenders' finest archer, also lamented his death.