My suggestion would be:
Caelum,
Rainbow sage (2-2-2-2-4-3-2-1)
Order 3
Prod 2
Death 3
Cold 2
Misfortune 3
Magic 3
Dom 5
Idea is to research evocation (2 for lightning bolt, 4 for thunder strike). Build 2nd fort ASAP to hire more mages. Against Niefel's it's easy, just enough screening troops to let your mages electrocute the giants. Against Helheim you need to recruit mammoths. They can hold for quite a while vs helherdings and let mages electrocute them. If you reach evo-4, things get pretty easy. Thunder strike is very effective.
The problem with this strategy is you just playing against Niefelheim/Helheim. If you meet somebody with mass of regular troops you're in trouble
