Wondering.
In Pokémon Black 2 and White 2, N returns to save Kyurem from Ghetsis riding Zekrom/Reshiram. When his legendary dragon is absorbed by Kyurem to transform to Black Kyurem/White Kyurem, he pleads the player to stop Ghetsis and get it back.
On Route 23 on the way to Victory Road, he will give the player HM05 (Waterfall). After the player has entered the Hall of Fame, N's Zoroark will appear on Victory Road and lead the player to the ruins of N's Castle, which N and the player walk around. In the throne room, N asks the player to battle him and his Zekrom/Reshiram. When the player defeats him, N reverts his dragon to its dormant state—the Dark Stone/Light Stone—and gives it to the player to summon it at Dragonspiral Tower to catch.
After catching or knocking out Zekrom/Reshiram, N arrives to congratulate the player and informs that Kyurem has returned to the Giant Chasm. From then on, N will appear in Nimbasa City near the Rondez-View Ferris Wheel on Fridays. After riding with him and having caught or knocked out Kyurem, he returns to the ruins of his castle, which now form part of Victory Road, for a rematch with different Pokémon depending on the season.
http://bulbapedia.bulbagarden.net/wiki/N
