New spells.

That’s very possible; I rarely play on the computer, only in campaigns and scenarios. Judging by what you said, I understand that this only works for Necropolis (the Dwarves don’t have enough resources to raise many units with the resurrection rune, and while Haven’s units benefit from light magic, they don’t have enough mana to use resurrection; Haven also benefits from light and life magic, but they don’t focus on summoning, so they don’t have a Hive. That leaves only Necropolis, because they focus on summoning and raising the dead – raising undead permanently, not just for the duration of the battle).