My sincerely thanks, brothers.
For the damage spell : Earth has none, while Air has a limited number of such spells, that including lightning bolt, orb lightning and (meh)shimmering fields, but sadly thunderstrike can't be cast underwater.
The point of MR is very useful, I'll get a number of kappas for gido to buy some time. Not sure how many mind lords the R'lyeh has(usually they'll buy one every turn they could, no?) so enslave mind may still be a trouble, but that's the best struggle I could anyway
About berserk+5, I think it just negates "Poor Amphibian" penalty that applies to my vanheres, while mind lords has a plenty of hp and aoe life drain and of course body ethereal
The idea of outflanking's just amazing. I'll do my best to be something more than a nuisance, prepare for that, tentacles! =D