Heart of Light is a common Enchantment — Aura card from Betrayers of Kamigawa (BOK), collector number 6. Current market price: $0.10 (foil $0.60), TCGplayer market prices via Scryfall.
Enchant creature (Target a creature as you cast this. This card enters attached to that creature.) Prevent all damage that would be dealt to and dealt by enchanted creature.