Kyurem, The Bounded Catalyst

Hexproof, Menace, Trample, Pressure. (Everything opponents cast besides commander costs {2} more to cast.)
When this card enters the battlefield and you
control Reshiram, Dragon of Flames, pay and extra {3}. If you do, put White Kyurem onto this card.
When this card enters the battlefield and you
control Zekrom, Dragon of Thunder, pay and extra {3}. If you do, put Black Kyurem onto this card.