Choose one —
• Counter target spell.
• You may choose new targets for target spell.
• Copy target instant or sorcery spell. You may choose new targets for the copy.
9/20/2016 If you choose new targets for the target spell or for the copy, the new targets must be legal.
9/20/2016 If you copy a spell, you control the copy.
9/20/2016 The third mode can copy any instant or sorcery spell, not just one with targets.
9/20/2016 The copy is created on the stack, so it’s not “cast.” Abilities that trigger when a player casts a spell won’t trigger.
9/20/2016 The copy will have the same targets as the spell it’s copying unless you choose new ones. You may change any number of the targets, including all of them or none of them. If, for one of the targets, you can’t choose a new legal target, then it remains unchanged (even if the current target is illegal).
9/20/2016 If the spell that’s copied is modal (that is, it says “Choose one —” or the like), the copy will have the same mode. A different mode cannot be chosen.
9/20/2016 If the spell that’s copied has an X whose value was determined as it was cast (like Eliminate the Competition does), the copy will have the same value of X.
9/20/2016 If the spell has damage divided as it was cast (like Chandra’s Pyrohelix), the division can’t be changed (although the targets receiving that damage still can).
9/20/2016 The controller of a copy can’t choose to pay any alternative or additional costs for the copy. However, effects based on any alternative or additional costs that were paid for the original spell are copied as though those same costs were paid for the copy.