Oracle Text

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.

Card Rulings

10/4/2004 Can remove as many counters per turn as you want to and this can be done at any time instants are legal.
10/4/2004 The cost that needs to be paid includes colored mana requirements.