Sky Tower

Final Floor: 34F
Unlock Method: Story Progession
Initial Level: -
Maximum Teammates: 3
Items: Yes
Check Map: Yes
Opponents Able to Join: Yes

You'll first encounter Rayquaza at the end of the main storyline. After climbing Sky Tower, it will battle you and you'll defeat it and ask for its help as a giant asteroid is heading towards the planet. When you return in the postgame, it will battle you again. In this battle, it will Mega Evolve. Defeat it and it will automatically recruit and give you the Stratos Lookout Camp