After you haev collected all of the other Johto badges, you can take Clair on for the final badge, the Rising Badge. But be forwarned she is the toughest Leader yet, with her Dragon Type Pokemon!
A clan of masters of Dragon-type Pokémon have lived in the city for generations. The masters built the Dragon's Den, a cavern with an underground lake that contains a shrine to Dragon Pokémon, as well as the elders of the Dragon clan. You can only come here after you haev defeated the Blackthorn Gym, but when you do you will find Trainer's who are willing to reward you for your accomplishments!