Psychic Allergy (The Dark 34) - Rare Magic:: The Gathering Card Magic: The Gathering Card

As this enchantment enters, choose a color.
At the beginning of each opponent's upkeep, this enchantment deals X damage to that player, where X is the number of nontoken permanents of the chosen color they control.
At the beginning of your upkeep, destroy this enchantment unless you sacrifice two Islands.