When the hero kills Na-Krul, he will always drop a Book of Apocalypse, a magic great sword, a magic war staff and a magic long war/battle bow. If the player opened his room by pulling the lever he would be a very tough opponent (except for the monk who would block almost every hit), possibly tougher than Diablo himself. However, if you read the books outside his room in the correct order he is rather pathetic - little, if any in the way of resistances and immunities, halved HP, lowered Armor Class, To-Hit % and damage.