Dr. Jekyll

When Dr. Jekyll enters the battlefield, the next spell you cast this game has madness. The madness cost is the same as that spell's mana cost. (When you discard a card with madness, discard it into exile. Then you can cast it for its madness cost or return it to your graveyard.)
At the beginning of each upkeep, if a player cast a spell using Madness, transform Dr. Jekyll.
Madness {1}{w/b}{w/b}