As mighty dragonstorms plunge Tarkir into turmoil and fierce dragons dominate the skies, the five clans join forces with their newfound Spirit Dragons in a battle for supremacy
This means you could spend the mana to activate an ability of an artifact you control or an artifact card in your hand or graveyard, for example
Vanille has both a black and green pip in her textbox, and could lead the deck by herself legally
For example, Orcish Bowmasters mutes the power of, say, Ponder, if you were to consider that in Modern, but that means decks with black and blue both get more powerful on one hand, and more inevitable on the other
The Great Henge A bit of a rogue entry on our list, since The Great Henge is a better green card draw spell than it is a powerful MTG mana ramp card
The color identity restriction means I'm excluding powerful transforming double-faced cards like Archangel Avacyn and Brutal Cathar since they have red backsides