Rhanva, the Shattered

Partner with The Paradox Heart
When you cast your first spell each turn, reveal
the top card of each players library. You may cast
a nonland card from among them, paying {w}{u}{b}{r}{g}, instead of its normal mana cost.
When you cast a spell using at least one mana of
each colour, add a mark counter to Rhanva, the Shattered. Then, if she has 3 or more counters,
exile her and return her to the battlefield transformed under her owners control.