Cerberus Guardian

When Cerberus Guardian enters the battlefield, you may choose a creature card in your hand. If you do, it perpetually gains “This creature enters the battlefield with an additional shield counter on it.” Otherwise, put a shield counter on Spara’s Bodyguard. (If it would be dealt damage or destroyed, remove a shield counter from it instead.) At the beginning of each combat, Cerberus Guardian gets +1/+1 until end of turn for each shield counter among other creatures you control.