[1.7.2] Derth Arena all stages oneshot

[Funk1245]

I accepted the arena quest, cast Soul Rot on the halfling, and for some reason killed all three enemies in one turn. The quest was completed as usual, but the arcane blade was still standing at the other end of the arena. He did nothing and just stood in one place. Every time I tried to hit him in melee, the log indicated that I killed him, although the actual NPC was still there. Weird!