Is there more than one nation below sea level in Etheria besides the hypothetical one sirens probably come from? If there are not, were they all wiped out at some point or something? Considering that in our world the majority of the surface is covered by ocean, etheria's geography is a lot like ours, and the oceans of our world have many diverse ecosystems, it would be awesome to see what kind of nations would arise underwater in Etheria. I bet there could be a crap-ton of different nations, races and mages we could get from underwater countries. for instance we could have some sort of manipulator/voodoo dark/mind Mage of a cephalopod race, kinda like Ursula from the little mermaid. Or we could have a water and lv1 nature Mage that gains fast on water terrain and gets stronger from eating living creatures, and focuses his playstyle on summoning prey under the enemy mages control, maybe prey that either deals damage to their controller, has upkeep effects or has "when this creature is destroyed" effects. Maybe it could be a necropian shark or something. And it would have to have bloodthirsty of course.
Thoughts?
I also just had the thought that any underwater Mages that are trained in fire would be an excuse for more steam and volcanic spells.
Also, I think that not all underwater mages would be trained in water in the same way that not all mages that live underground would be trained in earth, and not all mages that live in the clouds would be trained in air.