The Compendium of Alternate Formats, Entry Four: Rainbow Stairwell
Rainbow Stairwell is a format for a sixty-card deck. It can be built in a variety of ways, but the rules are similar. The main premise of the deck is that you have to use cards with a converted casting cost 1-6, one card of each cost in each color and artifacts. Gold cards are therefore disallowed.
So, for example, for your one drop, you could play Unsummon, Giant Growth, Mon’s Goblin Raiders, Dark Ritual, Healing Salve, and Soul Net as your six cards. It doesn’t matter how much mana is of that color, just the total converted casting cost. So a card like Silvos, Rogue Elemental, with its three Green in the casting cost, is just as good for your Green Six spot as Sulam Djinn, with its one Green. Six cards of each color plus artifacts, running from a cost of one through six. There are, as always, additional rules…