During two special level-up periods, receive great prizes via Challenge (Y) tab for leveling up your Archer:

• First level-up period: Dec. 12th, 2018 After Maintenance - Jan. 2nd, 2019 Before Maintenance
  
  • Get rewarded for reaching levels of 15, 25, 35, 45, and 55.
• Second level-up period: Dec. 19th, 2018 After Maintenance) - Jan. 16th, 2019 Before Maintenance
  
  • Get rewarded for reaching levels of 56, 57, and 58