Mirari

If the spell is countered before the triggered ability resolves, then the ability will make a copy of how the spell looked right before it was countered.

You are not required to choose new targets. If you do choose, then the targets must be legal. If you don’t change them, the spell is placed on the stack whether or not the targets are legal. The legality of the targets is always checked on resolution of the spell, so the spell may be countered at that time if all of its targets are illegal.

It triggers once per spell, so you can’t get multiple copies of a spell using this card. And since this card is legendary, you can’t control more than one.