ToME: the Tales of Maj'Eyal

I just faced a strange death.
I faced the Horned Horror with my shadowblade (nightmare difficulty), and never managed to hurt it.
All my blows where stopped by her armour, (up to 20 damage per hit blocked) whereas her armour (as mentionned in the description) was 3 (with 30% or armour hardiness).
And also it blocked my magical attacks (20 damage blocked on all spell attacks)

So I guess I probably missed something, but what ?!?

probably horned horror's class was brawler and they mitigate any damage by a flat amount of 15-30 points. your best bet should have been hitting for hitting with strong attacks instead of fast. displacement shield would have helped if nothing else.

Yeah, check next time to be sure but it was likely Striking Stance; it gives flat damage reduction. The Horned Horror got somewhat more menacing with the brawler buff.