Arlinn, Apex Predator

At the beginning of your end step, look at the top three cards of your library. Put up to one creature card with power less than Arlinn, Apex Predator from among them onto the battlefield. Put the rest on the bottom of your library in any order.
At the beginning of each upkeep, if a player cast two or more spells last turn, transform Arlinn, Apex Predator.