CreaturePump

As this enchantment enters, choose a creature type. Creatures you control are the chosen type. The same is true for creature spells you control and creature cards you own that aren't on the battlefield.

At the beginning of your upkeep, reveal the top card of your library. If it's a creature card that shares a creature type with a creature you control, you may cast it without paying its mana cost. If you don't cast it, put it on the bottom of your library.