Artifact, 2 (2) Imprint - When Isochron Scepter enters the battlefield, you may exile an instant card with converted mana cost 2 or less from your hand.
{2}, {T}: You may copy the exiled card. If you do, you may cast the copy without paying its mana cost.1
Illus. Mark Harrison
10/4/2004: If the imprinted card leaves the Exile zone while the ability to make a copy is on the stack, then no copy will be made.
10/4/2004: If this card leaves the battlefield while the ability to make a copy is on the stack, the ability will still make a copy using the last-known-information rule.
12/1/2004: Isochron Scepter's second ability creates a copy of the imprinted card in the Exile zone (that's where the imprinted Instant card is), then allows you to cast it without paying its mana cost.
12/1/2004: You cast the copy while this ability is resolving, and still on the stack. Normally, you're not allowed to cast spells or activate abilities at this time. Isochron Scepter's ability provides an exception.
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 may choose to cast either side of the split card, but not both. The split cards Fire/Ice, Illusion/Reality, Night/Day, Stand/Deliver, and Wax/Wane all have at least one side with converted mana cost 2 or less.)
12/1/2004: You can't cast the copy if an effect prevents you from casting Instants or from casting that particular Instant.
12/1/2004: You can't cast the copy unless all of its targets can be chosen.
12/1/2004: If you don't want to cast the copy, you can choose not to; the copy ceases to exist the next time state-based actions are checked.
3/1/2005: The creation of the copy and then the casting of the copy are both optional.
Mirrodin
(Uncommon)