A cube that involves the planar deck from Planechase. Draft the planes with the rest of the cards (You will have 18 cards per pack). You can either seed 3 planes per pack or make it truly random. While deckbuilding, you build a planar deck out of the planes you drafted. Your minimum planar deck size is 7 and you have no maximum number of phenomenons. Otherwise, the rules are identical to planechase rules with individual decks. The archetypes are as follows:
Azorius Stax
Boros Heroic (minor go wide theme)
Dimir Control (minor mill theme)
Golgari Dredge/Reanimator
Gruul Werewolves (minor go wide theme)
Izzet Carddraw (minor spellslinger theme)
Orzhov Aristocrats
Rakdos Aggro
Selesnya Ramp/Cheating out expensive stuff
Simic Flash (minor enchantment theme)