Defeat the Miren Fortress garrison with your companions and report the result to Rossjof.
Step 1. Defeat the Miren Fortress GarrisonA force of Elyos or Balaur that appear when Miren Fortress is Invulnerable. The Garrison is comprised of Fortress Snipers, Gallowglasses, Mages, and Priests. (x10).
Step 2. Report the result to RossjofA Centurion of the Red Hasia Legion at Miren Island. He is gruff but capable..