Not sure if bug, cheat or some absurdly OP item I never got my hands on. But once I got to around depth 80. Just about every single player ghost I faced had infinite multi strike. As in I would hit them down to like 20% HP with my first Whirlwind Blade Multi strike. Then they would just hit me however many times it took them to kill me. Just multi strike on top of multi strike until I died. Easily 4+ hits in a row most fights.