Vampires. Discussion.

which means you lose often......cerberi take them down pretty well, and if you're lucky, it's even better—three at once; and spawn are great at knocking out vampires who have the clip wings spell cast on them—and devils are wonderful in both attack and defense! It's cool that they can summon ice elementals!

I haven't played in a very long time, of course; I don't really like 4. But I didn't have any problems. I took ghosts simply because I liked them more. Vampires are definitely better than spawn; you can see it when comparing growth to growth in a duel. You say clip their wings, but what if we shut down the spawn's shooting? Devils clearly lost to dragons in terms of stats, and they didn't even get countered. Yes, they are convenient for taking down a hero, but after that... I'm not much of an expert; maybe you use some tactical tricks, but growth of ghosts, vampires, and dragons will win over cerberi, spawn, and devils in a simple battle (without heroes). And then there is Necromancer.