Merseine is a common Enchantment — Aura card from Fallen Empires (FEM), collector number 23b. Current market price: $0.15, TCGplayer market prices via Scryfall.
Enchant creature This Aura enters with three net counters on it. Enchanted creature doesn't untap during its controller's untap step if this Aura has a net counter on it. Pay enchanted creature's mana cost: Remove a net counter from this Aura. Only the controller of the enchanted creature may activate this ability.