What is a good underwater nation?
LA Atlantis. And it's not an UW nation!
UW nations are a peculiar breed. Disclaimer: I've never played in MP Pelagia/Oceania, only in SP tests or in "I play everyone for testing" SP games. Most UW nations are weak on the troops side, and have the massive advantage of being safe from rushers and having a ton of time for expansion. Plus, seas are quite rich in gems and you could build an effective research. Plus, UW Thrones. And Heat/Cold seems not to affect too much UW realms.
Furthermore, attacking UW foes that know what they are doing is hell. Some nations can work well UW like Agartha (sucks that you got them as foes) but they are a minority.
Prob is, UW nations pay with a worse pretender selection and subpar troops for aboveland conquest, and you
need aboveland conquests to be competitive (or with MA Atlantis to be adequate, even). So UW nations have a safe beginning but risk to be boxed him and forgotten while they slowly dimish to irrilevance.
Sure, some players find fun to go out with Globals from their UW bunkers, but Globals are not that game-winning, bar chaincasting Apocalypse and ruining the game for everyone.
"Good" UW nations to understand the basics are LA Atlantis, that is a tough as nails Aboveland faction with a more than adequate UW selection, MA R'lyeh, that has a good roster but requires some finesse, and
mayyybe MA Oceania. MA Xibalba can reach UW quite easily.
On the others:
EA R'lyeh: Huh. Next.
EA Therodos: Therodos is
not a UW nation. It's a nation that requires a huge amount of skill to be properly employed, and even in the case it can fail. Not for newbies, and not for UW fans.
EA Atlantis: baseline EA Atlantis is an expensive Ogre nation, with adequate troops (reef dwellers, Deep Ones) awesome mages but everything is slow and expensive as fug. I love it, but it's simply tastes. If you
can get a EA newbie game with you as the only UW power, EA Atlantis is a good bet. Research will be expensive though, take Magic scales.
EA Pelagia&EA Oceania: before, they were "Kill everything UW and then rot". Now, I don't know.
MA R'lyeh: Good for what it is. Next.
MA Xibalba: Never played with 'em. Blood/Death nations are not my favourite. Probably the worst Atlantean infantry, though.
MA Atlantis: Huh. Ehm. Huh. NEEEEEEEEEEEEXT. (Finding a way to play MA Atlantis is a dream of mine.)
MA Pelagia&MA Oceania: Don't know again.
LA R'lyeh: MA R'lyeh with domkill and chaff you have to pay for. Not newbie friendly.
Never fought it in MP.
LA Atlantis: Aboveland nation. It's good.
Other nations have UW summons or UW troops (Agartha, LA Jomon, LA Xibalba) but they are not so focused. But again, after getting a good land claim you can switch to UW conquests and enjoy the spoils, always nice.
sleep cloud works under water?
Yes. UW combat is buff/HtH land though. Evos work, but it's always a slog.
what to do against astral something and mind blast?
Antimagic is a good counter, if you have it. Mind Blasters are outright godly against newbs/unprepared opponents thanks to their range and focus, but they are somewhat easy to negate for the experienced player. They lose a lot of steam after the earlygame, though, even if they are excellent indie clearers.
But you are against 56 Mercuries. You are, bluntly put, dead.
I'm playing Oceania right now in Decline7. Cloud the waters with sharks, swarms and elementals(both bottles and summons), then spam the fatigue spells you get with W/N. Numbness, Encase in Ice, Sleep Cloud. Then throw some panics on top. It's not amazing, but if the battle lasts long enough maybe you can wear them out. Too bad you probably don't have Shark Attack/Foul Vapors, or even Bone Melter. Though the mercuries MR is pretty good. Then again, he is probably out of time.
Yeah that can happen if you are constantly at war.
