Referring back to the original post,
I would recommend either the Saboteur or Infector as your main class (I haven't played Shadowmancer yet) . Jaded Bacon already talked about Saboteur, but he failed to mention "Curse of the Monkey God". Frankly I think this card is one of the best Number 2 overlord cards in the game. Not only is it hilarious to see the heroes faces when one of their comrades is changed into a monkey, it also gives you a turn to kill a hero (as they cannot attack or roll defense dice). Combined with a "Web Trap", "Curse of the Monkey God" is amazing; I speak from experience when I say that immoblizied monkeys are the way to go.
As far Infector, you really should be playing longer two encounter quests with this class. I am currently in a LoR campaign and Infector is working out quite well. I started with "Contaminated" and moved on to things such as "Airborne", "Tainted Blow", and "Dark Host".
After getting most or all of the cards in your main class, I like to buy a few "Blood Rage" cards and maybe some other cheap ones.
I hope this helps!