Vivien, Monsters' Advocate

You may look at the top card of your library any time. You may cast creature spells from the top of your library. [+1]: Create a 3/3 green Beast creature token. Put your choice of a vigilance counter, a reach counter, or a trample counter on it. [-2]: When you cast your next creature spell this turn, search your library for a creature card with lesser converted mana cost, put it onto the battlefield, then shuffle your library.