In Heroes 5, there is a neutral magic school that has no equal in terms of damage and also ignores magic resistance. It is similar to chaos magic. It includes the spells "Devil's Chain" and "Hellfire." One drawback is that it doesn't affect demons. Unfortunately, summoning magic is only available to wizards and necromancers. For the former, phoenix, elementals, and celestial shield act as a "boost" to military strength; for the latter, it's raising the dead. Wizards benefit the most, and the reason is that they have a lot of mana (and summoning is the most mana-intensive school) and strong spellcasting. Demons and elves are also quite knowledgeable, but they are not very good at spellcasting. Dwarves and humans are inferior in all respects. Unless dwarves need summoning for a super ability. There are no inherently strong or weak schools here; it's important who uses the school and how well it suits them.