Mantle of Leadership is a uncommon Enchantment — Aura card from Planar Chaos (PLC), collector number 9. Current market price: $0.29 (foil $1.22), TCGplayer market prices via Scryfall.
Flash (You may cast this spell any time you could cast an instant.) Enchant creature Whenever a creature enters, enchanted creature gets +2/+2 until end of turn.