The most difficult alternative

Life: pikemen, monks, archers
Death: ghosts, fiends (we'll gather them using necromancy), devils (ice demons tank well and remove debuffs + teleportation)
Nature: I haven't played much, so I can't say.
Chaos: medusas, ifrits, dragons
Barbarians: Cyclops.
Haven: golems, djinns, titans/dragons depending on resources, I would prefer dragons.