Enchant creature
Merseine enters the battlefield with three net counters on it.
Enchanted creature doesn't untap during its controller's untap step if Merseine has a net counter on it.
Pay enchanted creature's mana cost: Remove a net counter from Merseine. Only the controller of the enchanted creature may activate this ability.
Can remove as many counters per turn as you want to and this can be done at any time instants are legal.
The cost that needs to be paid includes colored mana requirements.