Contractual Safeguard is a rare Instant card from New Capenna Commander (NCC), collector number 115. Current market price: $3.41, TCGplayer market prices via Scryfall.
Addendum — If you cast this spell during your main phase, put a shield counter on a creature you control. (If it would be dealt damage or destroyed, remove a shield counter from it instead.) Choose a kind of counter on a creature you control. Put a counter of that kind on each other creature you control.