What is the source of the Mages’ power?

I also had the idea to give magical protection to the mage troops using mini-art, take Jalib as the hero, and cast Armageddons, but testing showed that Armageddon is ridiculously weak for mages, and the spell itself isn't always available in the castle. Also, Jalib's "Spell Reversal" doesn't reflect Armageddon.