Tidal Influence

Cast this spell only if no permanents named Tidal Influence are on the battlefield.
This enchantment enters with a tide counter on it.
At the beginning of your upkeep, put a tide counter on this enchantment.
As long as there is exactly one tide counter on this enchantment, all blue creatures get -2/-0.
As long as there are exactly three tide counters on this enchantment, all blue creatures get +2/+0.
Whenever there are four or more tide counters on this enchantment, remove all tide counters from it.