This set is about a conflict between the humans, elves/treefolk, and merfolk/ faeries. I'm trying not to do overt tribal things to avoid tromping on the toes of Lorwyn.
The factions are organized into enemy color triads, though there aren't any multicolor cards except a few mythics, as has been a tradition in recent sets. Instead, cards have off-color kicker and activated ability costs.
Humans are white, with blue and red costs.
Elves are green, with white and black costs.
Merfolk are blue, with black and green costs.
Centaurs are red, with green and blue costs. I haven't put any cards from the other factions on Multiverse yet. This is because I have a decision to make. I'm making a less-than-conventional set structure, with very few cards in each set and four sets to a block. This is because I'm not really trying to emulate Wizard's current block model, but rather tell a vague story and practice at making sets. The story is mainly based on the character of Marthanos as he develops and eventually becomes a planeswalker.
The choice I face right now is this: I'm considering not including black in the first set, and possibly red as well. Both colors are included in payments, but I might not make cards of those colors. I can't decide whether or not this is a really bad idea. It mainly springs from the story, where the red and black factions don't really appear until later. Can I receive some thoughts on this?