Barmmyte, Sensor of Woe

When Barmmyte enters the battlefield, choose a player.
Barmmyte enters the battlefield with a -1/-1 counter on it for each card in chosen player's hand.
Whenever a creature controlled by the chosen player attacks you, remove a -1/-1 counter from Barmmyte. That player discards cards until the number of cards in their hand is equal to the number of counters on Barmmyte.