Worldbuilding - Aquas

Welcome to our first cooperative worldbuilding! I'll be asking for feedback every step of the way, so please contribute. And I want any artists out there to draw some concept art for me – I'll post everything that I get at the beginning of each post. Ready to start? Then hit the jump!

For this world, I thought it would be interesting to have a world where the existence of planeswalkers is well known and accepted. However, I don't want anything so boring as some ancient planeswalker revealed himself successfully, so we need something about the nature of the plane that makes it so planeswalkers can't hide their nature. So, what if the plane is entirely underwater? With the new planeswalkers not being godlike shapeshifters, they have to breathe and stuff, and a bunch of strange creatures suddenly appearing dead would (eventually) make people realize something's up. So, with that in mind, the temporary name for our underwater plane will be Aquas, named after a planet in Star Fox (Any other name suggestions are welcomed)

Normally, we would have humans as the primary race on the plane, spanning all five colors. But merfolk are just humans with fish tails, so let's have them be our primary race. That means that the merfolk here have to fill the role that humans do in every other plane – they are small to medium creatures that establish the baseline of what each color does. I imagine that the Blue merfolk will look the most traditional of the various kinds, but we'll get to that later.

For now we have to establish a few other things. First off, creatures can't really fly underwater, but we still need an evasion ability for the purposes of card design. While this world would likely never get a card set to go with it, we'll try our best. Anyway! Our options for evasion abilities are: Unblockable, landwalk, Shadow, Protection. Unblockable is difficult to work around – the same with landwalk and Protection. Therefore, let's go with Shadow. The initial flavor I've got in mind is becoming the water or something similar.

What do the five basic land types translate to underwater? Plains could be the kelp fields. I don't know about Islands or Swamps – suggestions? Perhaps Swamps could be the trenches? Mountains would be the volcanic vents and the areas around them, while Forests will be coral reefs.

So, for today we need: Different land types, Shadow, and merfolk. I also need ideas as to how the various colors will react to planeswalkers, along with ideas for different races to use in the five colors. I'll post what I get tonight (or tomorrow, whichever) I'm moving the evening posts to 6PM to give people more time.