Since I am role playing my character this way, I wanted to trap Manni's soul in a black soul gem. I am not sure if this is possible, however I tried my 60 sec soul-trap (named Mamon's shadowed claw) and saw no result. It is very possible the spell ran out before his death.

Is this possible at all? (may have to try again)

Ah, I got it. Used his Staff of Worms to reanimate, cast the soul trap and I got his soul!

Glad I could help.

I realize this is off-topic,but why is Mannimarco so super weak?
Any necromancer in his cave is far more dangerous than him.Ive seen mudcrabs more fiercer than him.

http://gamall-ida.com/f/files/realmannimarco_190.jpg