[Micah]

Amorphous - I think the comparison to Yomi is a better one than to Niefel. And Yomi isn't generally regarded as a superstar nation.

Apart from that you are giving way too much credit to the mage of the deep. They're pretty much irredeemably horrible. They're massively overpriced, can't cast antimagic like you say without some sort of boosting (cons-6 for skullcaps? Good luck with that. POTS? You're dead to a magic duel before you get to your 2nd round even on defense, plus antimagic requires a detour up enchantment research-wise, which has little else of much use to Atlantis) and are magic-duel fodder if you can somehow last long enough to even get to them, especially since you're having to spend 1000g to get a single point of astral on average. Their non-sacred status also means they're an upkeep sink with their insane pricetag. W2 as their base is also incredibly uninspiring.

The other major issue fighting rlyeh is that their mind blasters tend to get away fairly intact if they lose a battle, meaning they're around the next turn with a fresh screen of PD chaff to hide behind, whereas Atlantis' troops have to get up close and personal to do much of note, and thus take a large beating in every engagement even if they win.