On his defeat, Drayden thanks you for a difficult battle, pointing out that one of the major points of pokemon battling is to work together with others to meet challenges.  Making note that you now have seven of the Unovan badges, Drayden also hands you TM82, which contains the move Dragon Tail.  This 90-accuracy Physical move has a -6 priority, making it one of the slowest moves in the entire game.  The Dragon-type attack is a decent 60 power attack with the side effect of immediately forcing the hit pokemon to switch out of battle if there is any other pokemon on its team.  This is not always the most useful thing (particularly pointless against wild pokemon) but it can be vastly effective against trainers, particularly when combined with entry hazards like Spikes and Stealth Rock.

He then tells you to head outside to wait for him, so he can tell you about the legendary Dragon-type pokemon.

Somehow, despite having been left behind on the head of the vertical dragon statue, Drayden is immediately behind you on your way out of the gym.  He tells you that he’ll ‘show you the way’, heading around town to just outside his house, where he waits beside the Pokemon Center.  Once you step up to him, he reiterates his direction to follow and heads into his home.  Follow him in and he’ll stand in the middle of the room with you and begin.

According to Drayden, the two dragon pokemon were awakened two years ago, each pursuing their own goals.  Zekrom sought what is ideal to inspire hope in the world, and Reshiram sought what is true with the intent to convert the world to ‘goodness’.  According to Drayden, the two were originally one pokemon, forced to split by the two heroes who helped it during the origin of the Unova region who fought to prove themselves more correct than one another and tore the area apart.  Although the concepts of ideals and truth aren’t actually opposed, the legendary pokemon tore itself apart to follow both paths.