Playing a Meridia-favorable high elf and trying to avoid raising the "people killed" stat above zero; spammed lightning bolts while drinking tonnes of restore potions of all sorts, then dual-cast fury on him when his health was way down and let him turn on (and get murdered by) his own corrupted shades. Takes a pretty high illusion though.
The subsequent Malkoran's Shade was subsequently dispatched by looting the ice storm staff from his mortal remains and just wailing on him with his own magic. At that point my character had no compunctions. 🙂
Basically I picked of the shades with my bow, then knocked him off his feet with unrelenting force, i just beat him to death with the warhammer you get from The Cursed Tribe quest. His shade was easy, i didn't even need to heal.