Leyline of Transformation (Duskmourn: House of Horror Promos 63s) - Date Stamped - Rare Magic: The Gathering Card

If this card is in your opening hand, you may begin the game with it on the battlefield.
As this enchantment enters, choose a creature type.
Creatures you control are the chosen type in addition to their other types. The same is true for creature spells you control and creature cards you own that aren't on the battlefield.