"His father defended Peak Pass against numerous attacks but when the forces of the Chaos Dwarfs entered the conflict, he was unable to hold any longer. Hearing of the death of Garagrim, Ungrim took upon himself the Slayer Oath once again, thereby merging his oath as king and his oath to seek death."
I realise they're both said together, but the way it's written, it seems like two separate thoughts. He couldn't defend Peak Pass, which sucked, but then he heard about Garagrim's death and instantly re-took the slayers oath? Was it a cumulative thing? Peak Pass + dead son? But why should Garagrim even be an influence, he just died so Ungrim wouldn't have to do what he did.
The whole thing lacks consistency to me.