Fusion Rules

All Fusion creatures have the same colors
and converted mana costs as all creatures used in
their requirements combined. To put Fusion creatures
onto your battlefield from outside the game, first you
must cast Polymerization or a card that mentions
putting Fusions onto the battlefield from outside the
game. Then you discard or sacrifice any cards from
your hand or field that are mentioned in the Fusion
card's requirements. After that, you put it onto the
battlefield under your control. Putting