Composite Shield

Once as a reaction to being targeted by a spell or
attack. A shield of opalized wood materializes
between you and an attacker. You gain +3 to AC
or, advantage on a save, against the triggering
attack or spell.
Afterwards: The shield lands at your feet.
Composite Shield: A magic shield granting +3 to
AC. Once per long rest, as a reaction, gain
advantage vs the triggering spell.
After using, destroy this card. (Or keep it I guess?)