Quest for the Holy Relic is a uncommon Enchantment card from The List (PLST), collector number ZEN-33. Current market price: $0.23, TCGplayer market prices via Scryfall.
Whenever you cast a creature spell, you may put a quest counter on this enchantment. Remove five quest counters from this enchantment and sacrifice it: Search your library for an Equipment card, put it onto the battlefield, attach it to a creature you control, then shuffle.