Heimerdinger, the Inventor

When Heimerdinger enters the battlefield, create three 1/1 colorless Turret artifact creature tokens with haste. You can only control up to three Turrets at a time. Whenever Heimerdinger attacks, put a +1/+1 counter on a Turret you control (max four). If a Turret has four +1/+1 counters on it, you may sacrifice it and create a 5/5 colorless Apex artifact creature with double strike, haste, and shroud. If you do, sacrifice it during the beginning of your next upkeep.