Challenger badge is earned by completing events. The more events you participate in and finish, the higher your badge level becomes. 

Note: Treasure hunt events are excluded.

• Completing 1 event earns you the bronze badge.
• Completing 5 events earns you the silver badge.
• Completing 20 events earns you the gold badge.
• Completing 50 events earns you the ruby badge.

Please click the following link for more details about the badges you can earn and their requirements:
https://blog.jawaker.com/jawakerbadges-en/