At some point during the events of Black and White 2, Ghetsis (the leader of Team Plasma) captures Kyurem. Along with the sage Zinzolin and the scientist Colress, he harnesses its power to control the Plasma Frigate -- the ship that serves as Team Plasma's base of operations. He later uses Kyurem's ice powers to freeze Opelucid City and invade it. While Gym Leader Drayden is distracted by grunts, the Shadow Triad steals the DNA Splicers and gives them to Ghetsis.
When the player confronts Ghetsis in the Giant Chasm, he attempts to kill them with Kyurem (who has been removed from the Plasma Frigate). Pokemon Trainer N intervenes with his Zekrom or Reshiram, depending on the version, and saves the player at the last second. He attempts to bring down Ghetsis, but Kyurem proves too powerful, and N's legendary dragon succumbs.
Ghetsis then fuses Kyurem and Zekrom/Reshiram using the DNA Splicers to create Black or White Kyurem. It then attacks the player in battle, and it must be defeated to split it into two dragons again.
After the player has Kyurem and Zekrom/Reshiram in the party and the DNA Splicers in the bag, they may fuse Kyurem at any time.
