[Vynd]

A Wraith Sword causes you to get fatigued when it hits you. So that might have been where your fatigue was coming from. It is also possible that you were affected by, say, a chill or a heat aura, from some other equipment that Bogus was wearing or from a spell that was cast at some point.

In any event, once your fatigue goes over 100 you're unconscious. Meaning that you won't fight back and are much easier to hit. Your fatigue will recover faster when you're unconscious, but obviously something was counteracting that. Once your fatigue exceeds 200, you start taking damage and most likely die in short order.

I've never had the pleasure of meeting Bogus the Troll and his merry band, but I gather that he's as tough as they come. Your running into him was decidedly bad luck.