Doctor Maro

Before the start of the game, assemble an experiment board of any color identity. (Experiment board contains up to 20 creature cards with mutate).
Creatures you control have mutate. Their mutate cost is equal to their converted mana cost plus {g/u}{g/u}.
When a creature mutates in this way, roll a d20. On a 20, you may choose an effect from your experiment board. Otherwise, your opponent chooses an effect at random.