Curse of Biting Rats

Enchant Player
At the beginning of each upkeep enchanted player
creates a 1/1 black rat token that has
"At the beginning of each upkeep this
creature deals 1 damage to its controller.".
Enchanted player may pay {1} at any time, if
they do that player sacrifices a rat they control.
"Evil infests the soul like rats infest a storehouse."
-Common Innistrad saying.