[Taqwus]

Water mages should be kept separate, for now. Death mages present a similar risk, although in practice I've seen less Soul Vortex casting and more summoning from them when unscripted so the risk is probably much less in practice.
And never, ever take a nature mage into battle alongside your Abysian army, lest he cast Protection on one of your Abysian commanders lowering his fire resistance by 25%.