Berry Frost, the Bittercold

Snow Balling - At the beginning of your upkeep, if you don't control a white snowball artifact token, create a white snowball artifact token with shroud.
At the beginning of your end step, put a snowball counter on target snowball artifact token. Then that artifact deals 1 damage to target opponent for each snowball counter on it. When a snowball artifact token has 4 snowball counters on it, destroy it.