Ashikaga Takauji, , is the Samurai quest nemesis. He wields the Tsurugi of Muramasa, and can therefore kill you in one hit. This, along with the fact that he ignores Elbereth, makes him one of the most dangerous quest nemeses, though his attacks other than the Tsurugi are unexceptional. The easiest way to kill him is to zap him with a wand of death, which you may be able to obtain from a monster on the quest (attack wands are plentiful).