Planes of existence was good thing in MoM. I did like to play the dark elves.

Yeah I was going to post a whole new reply comparing this game to Master of Magic.  Sounds like a more highly evolved version.

This game along with Beyond Protocol, the new era of Master of Orion and MAster of Magic. =-)

NO!  not caves, we shoud have alternate planes of existant Master of Magic style.  Everybody uses underground.   I mean, I wouldn't mind underground (since really the programing for it is the exact same as alternate planes, you'd just have different terrain doodats and stuff) but I REALLY want alternate worlds of existance.

What about underground not as a "go there and explore" but as an alternate place to expand? I too don't want Elemental to feature massive attention in "hero" units but I'd love to be able to play a underground dwelling civilization, think Dwarves/Dark Elves.

That could be achieved by creating a underground "plane" with minimal (and empty) caverns and water sources (underground rivers and lakes) and letting the player, if he so chooses, to create a underground race who builds up it's town or fortress underground instead of above ground.

The same could be said about a naga/triton sea dwelling race, etc. I'm not sure Elemental is going for a High Fantasy approach or a more simple Fantasy approach but having several planes where one can grow it's own specific an UNIQUE civilization only adds more depth and replayability to the game.

Same here. Think about it: a "Hellish" plane, a "Heavenly" plane, and "Elemental" planes (Air,Water, Fire, Earth, Magic) each accessible via gates or portals, which could only be opened under specific conditions, effectively bottlenecking (or not) a player. That and culture/race/civilization customization would make Elemental a truly groundbreaking game.

I surely don't want to see any computer version of dungeon crawling as a part of this game. I disliked that stuff more than enough when I could work around it as an in-person RPG player. Until we have AIs truly worth the name, I don't want a computer game to pretend that it can emulate a good human RPG GM. Emulating second-rate refs might be a good place to start, however.

I'd love to see a limited underground in this game. By limited I mean I don't want there to be a vast network of tunnels and caves that essentially connect the entire map, like in a lot of maps in HoMM. But I think it would be really cool if there could be some tunnels or large caverns under mountain ranges or even passages underwater to islands.

I like the idea for a lot of reasons. It would add a lot of character to the world, and add tons of strategic options. Tunnels could allow for surprise attacks and quicker travel through tough terrain (and maybe have their own limitations), as well as mining opportunities. Underground fortifications in caverns could be exceptionally harder to conquer than counterparts above ground. Some types of beasts or other neutrals could make their homes underground. How cool would it be to establish your very own Kingdom under the Mountain, or mines of Moria?

On the other hand, I'm not that big a fan of dimensional planes. They're usually just... another world map. The biggest differences between other planes and the normal world are usually (always) visual - swirly lights and alien plants, plus some small side effects here and there. So troops without the Shadowalker ability are a little weaker in the shadow plane, or maybe fire magic will be a little stronger in the fire plane... In the end, other planes never really feel particularly special because they don't differentiate themselves enough from the regular world. And I haven't ever heard a particularly good way to make other planes feel that different, either...

I especially dislike the idea of elemental planes - one for each element. Seriously, I really don't want to have to keep track of what's happening in half a dozen different world maps. Not to mention, if the effects of each plane are relatively minor, then having so many would get downright tedious. And if the effects of each plane are significant enough for all those planes to play very differently, they could be exploited. If fire magic reigns supreme in the Fire Plane, a fire-specialized channeler hiding out in the Fire Plane would be almost impossible to beat militarily by anyone who didn't focus on fire magic.

I'd much rather see a well-implemented, limited and strategic underground than dimensional planes. The only reason I ever included big undergrounds in HoMM or the shadow plane in AoW:SM was to make the maps bigger, for a longer game. Happily, it seems that we'll be able to create insanely huge maps in Elemental, so that incentive is gone, at least for me. Personally I think a good underground would add MUCH more flavor and more interesting strategy than other planes.

Okay, for alternate planes:

Fey Dreamworld: doesn't link 1:1 with real world.  Allows for the planar navigator to enter Fey and make a shorter journey for their army.  I'm thinking mists of Avalon, with the Brothers Grimm and other not-nice fairy tale inhabitants.

Underwater/Underground:  It sounds like these will need to be optional for some players, like a built-in mod.  But I wholy support both of these.  The hardest part (for me) is someone who HATES the dwarves tunneling into the sea rather than fight them.  Mer-dwarves, brrr....

Shadow World:  C'mon, we gotta have this one to honor all the things that go bump in the night.  It also allows a realm for Lovecraftian critters to meander out of.

Elemental Forge:  I envision a realm filled with hot lava, ice flows, quicksand-gravel pits - a place where only heroes and magical units can survive.  But OH, look at the mana!  (And wandering weather conditions that rip the souls out of flying units.)

Gehenna:  While most religions disagree on the makeup, all of them believe in a realm where the demonic and diabolic live, in large fortresses of basaltic rock.  A place to summon demons from, and for the TRULY evil to build their elite troops. 

Which lead to: if you can summon something, you ought to have a place it's summoned FROM.  This is why I don't work in game design; simple ideas lead to mammoth projects.  (Which nobody else wants to work on.)

Honestly, I'd be happy with a 'these are the options for multiple maps, this is how to implement them'.  I could work wonders with just that, and an artist insane enough to attempt to build an alternate world.