Kithkin Armor is a common Enchantment — Aura card from Weatherlight (WTH), collector number 19. Current market price: $0.13, TCGplayer market prices via Scryfall.
Enchant creature Enchanted creature can't be blocked by creatures with power 3 or greater. Sacrifice this Aura: The next time a source of your choice would deal damage to enchanted creature this turn, prevent that damage.