Aspiring Rune Master.

The transformation into a divine entity allowed the heroic spirits to become aware of an alternative form of strength when the giants of Order needed it the most. 

Giants of Order are immune to spells, so they can't cast them. That's an acceptable trade. But their anti-magic domain went further than that. It not only destroyed their environment, but it also destroyed mana artifacts, magic weapons, and magic equipment.

It meant that they couldn't use mana equipment as mana entities and their infertile environment forced them to migrate often. Migration caused conflicts which quickly escalated to war. It is one thing to be able to turn an environment into a desert but Origin water in origin streams was also affected.