[Taqwus]

'Opposition' is the targeted anti-magic-unit spell; resist or take damage. It's also the effect on Elf Bane. Moon Blade does additional damage to magic creatures, but doesn't attempt Opposition, if memory serves.

Earth Attack is powerful for the marginal gem cost, which is presumably why it takes an E5 caster and a fair amount of research. Body Ethereal will help a human-sized victim, because earth elementals attack smaller targets by trampling, but this doesn't help against Ashen Angels because the latter use magic weapons IIRC.

Decoys make sense. So might a dome spell, to reduce the likelihood that the spell attacks will actually work, if this is a situation where you're getting pummeled in one province.