Spellbinder | Magic: The Gathering
Formats Spellbinder is Legal in
Official Oracle Text for Spellbinder
Whenever equipped creature deals combat damage to a player, you may copy the exiled card. If you do, you may cast the copy without paying its mana cost.
Official Rulings for Spellbinder
12/1/2004 : You don't pay the spell's mana cost. If the spell has X in its mana cost, X is 0. You do pay any additional costs for that spell. You can't use any alternative costs.
12/1/2004 : If the copied card is a split card, you choose which one side of it to cast, but you can't cast both sides. You can choose the other side later in the game, though.
12/1/2004 : Spellbinder imprints a card only once, when it enters the battlefield. Attaching Spellbinder to a creature doesn't trigger its enters-the-battlefield ability.
3/1/2005 : The creation of the copy and then the casting of the copy are both optional.