For what it's worth, the revealed characters are:
-Nicol Bolas, arguably the main villain. He's a scheming ancient dragon wizard and will definitely be black/red or black/blue. In Magic he's all three (black, red, and blue) so I imagine he'll be Chinese-like, probably with a three-color board change and leader skill activation.
-Chandra Nalaar, one of the main heroes. She's a fire mage and has basically no other traits or aspects. She'll definitely be red, will probably make red, and will probably need a lot of red.
-The Skyship Weatherlight, which is a flying boat. It will be white and probably will have a rainbow leader skill and/or active. It might be an equipment.
Honestly more than anything else I'm really curious to see what the filler enemies in the dungeon are going to be...