Wyverns

Of course, paladins are effective against the undead – that’s obvious. But there’s a catch. If you use the Necromancer’s “Undead Raising” ability, you can quickly eliminate the skeletons after they’ve been killed. After that, there will be no one left to raise.
By the way, here’s an interesting fact: paladins cannot be close relatives of dragons because dragons have 6 pairs of limbs, while paladins have only 4.
I always use paladins, ever since Dark Messiah – I like them :) It’s a pity they don’t have a “fury” ability.