Unbreakable Formation is a rare Instant card from Ravnica Allegiance Promos (PRNA), collector number 29p. Current market price: $1.51 (foil $2.25), 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.