This is more of a novelty idea cube that's built with only cards with cmc 4 or greater.
Work in progress.

Lately, I've been doing some more tweaking and may go a route of you win games by being the most mana-efficient with your expensive spells through unexpected means to try to break the expected mold of each play casts one spell per turn. Therefore may also try not to have any too high impact game swinging high drops.