To me the demons of that book are most definetly not the demons of dominions. His power revolves around 'electrodirection' which sounds like patent air magic to me
He would of course be immortal, as would be Taraka and Yama.
I was actually considering not making them mages at all (since they are all very specialized in their abilities). Instead i would give him a bonus shockwave attack and a built in weapon that lets him thunderstrike. It could be done either way though.
One of the national units would be the Master of Karma (body merchant) who would have the ability to heal afflictions ala arco priestess.