Snapback Spirit

Flash
Snapback Spirit has hexproof, defender, indestructible and can't block as long as it's face down.
Snapback Spirit enters the battlefield face down.
At the beginning of each player's upkeep, put a strike counter on Snapback Spirit. If this would result in there being two or more strike counters on Snapback Spirit, sacrifice it if it's your turn.
{t}, turn Snapback Spirit face up and remove a strike counter from it: Snapback Spirit deals 5 damage to any target. Turn it face down.