Protector Stalker

First Strike, Lifelink, Vigilance While this creature is on the battlefield, commander creatures opponents control get -3/-3 and commander creatures you control get +2/+2 and Indestructible. When this creature attacks, it gains Trample and +2/+2 for each commander creature on the battlefield and your command zone. When this creature leaves the battlefield, search your library for an Instant or Sorcery, add it to your hand. You may cast it this turn without paying its mana cost.