Duty Beyond Death is a rare Instant card from Secret Lair Drop (SLD), collector number 2387. Current market price: $1.92 (foil $2.61), TCGplayer market prices via Scryfall.
As an additional cost to cast this spell, sacrifice a creature. Creatures you control gain indestructible until end of turn. Put a +1/+1 counter on each creature you control. (Damage and effects that say "destroy" don't destroy those creatures.)