Unbreakable Formation is a rare Instant card from Secret Lair Drop (SLD), collector number 310. Current market price: $3.13 (foil $2.82), TCGplayer market prices via Scryfall.
Creatures you control gain indestructible until end of turn. Addendum — If you cast this spell during your main phase, put a +1/+1 counter on each of those creatures and they gain vigilance until end of turn.