Help Killing A mark Please!

The Bitch’s name is Deathscythe.
All my characters are all levelled up pretty good, but i just got the "Game Over"
sign on my screen.
After a while, the only magic that seemed to work was "Shock" and he was amune to me hacking away at him, so any ideas gratefully received!

Deathscythe…the Reaper in the Necrohol of Nabudis? He’s quite easy if you confuse him when he becomes immune to physical damage – he’ll keep hitting himself, without removing the ailment since he’s immune to the damage. You’ll have to renew this periodically, and it might take a few tries to inflict the ailment, but it will give you time to attack with Shock (best magic to use, as you seem to already know).