Your opponent wont have enough mana to drop a 5- or 6-mana planeswalker and pay an extra 4 mana
@_PREMIUMBANDAI_ pre-orders shipping this month
During your Battlephase, if this card makes a second attack, destroy the opponents monster before the damage step
While we have seen previous variations of the fabled three birds (Zapdos, Moltres, and Articuno) before, this has got to be one of the coolest in terms of artwork
Two immediate options that come to mind are Jodah, Archmage Eternal, which basically lets you cast this for WUBRG and then net yourself 5 mana to help cast the spells you reveal, and Mizzix of the Izmagnus, which can cast this 10cmc spell for as low as RRR
Most of an Opt for not-necessarily-Blue mana