When Chittering Witch enters the battlefield, create a number of 1/1 black Rat creature tokens equal to the number of opponents you have.
{1}{B}, Sacrifice a creature: Target creature gets -2/-2 until end of turn.
In a multiplayer game, opponents who have left the game aren't counted by Chittering Witch's triggered ability.
You can sacrifice Chittering Witch to pay the cost of its last ability.