[Heironeous]

One of the really nice things about Machaka is that you have a lot of flexibility in terms of magic. I'd have to second tinkthank's recommendation of magma eruption - it can really put enemies in a world of hurt.

However, I also like the Conjuration path for Machaka. Conj 3 gives you summon earthpower and phoenix power (+1 earth and fire respectively), and higher levels provide lots of nasty summons to strengthen your armies. I particularly like the commander summons, e.g. bane lord, as Machakan mages can forge all sorts of gear to turn them into killing machines.