Well, Shadow Magic for me
I love the way you capture souls, with the quote from Mortal Kombat lol.
Plus, it's nice to play with souls and those dark spells
Summoning Daemon is quite tricky and dangerous, but funny especially when they are released.
I also plan on dabbling into Divine Magic, being a follower of DEA'LELIATH, more dark spells for me
And also might be useful when running out of souls, though finding a Holy Ground consecrated to DEA'LELIATH in the human territories would be hard, thus making the refueling of Faith difficult as well
But evil chars are so much fun to play out, difficulty is just a part that makes the whole thing even more pleasurable.