Weakstone's Subjugation is a common Enchantment — Aura card from The Brothers' War (BRO), collector number 72. Current market price: $0.11 (foil $0.21), TCGplayer market prices via Scryfall.
Enchant artifact or creature When this Aura enters, you may pay {3}. If you do, tap enchanted permanent. Enchanted permanent doesn't untap during its controller's untap step.