The Pillaging Skeletons could pick everything up, take over 4 territories, get 2 extra monsters, still get 8 gold because of pillaging, have 4 large stacks of monsters (large investment to only kill 1 skeleton), and the 8 gold/turn was still good because the player held EVERYONE else down to less than that by getting rid of 4 enemy tokens every turn.
Dragon Elves were the only combo we found to keep the Pillaging Skeletons from running away with the game, killing 2 skeletons a turn easy (sometimes 3 with a good roll), and never losing any. Are there any other counters?
Extra Kudos for staying away from "Everyone cooperatively attack the skeletons!", as my group doesn't like to just gang up on someone :)