Energy Vortex

As this enchantment enters, choose an opponent.
At the beginning of your upkeep, remove all vortex counters from this enchantment.
At the beginning of the chosen player's upkeep, this enchantment deals 3 damage to that player unless they pay for each vortex counter on this enchantment.
: Put X vortex counters on this enchantment. Activate only during your upkeep.