Dying Light: How to get into Rais’s Garrison, The Pit Story Mission (Climb to the Roof Entrance)
Level 1 and 2 Garrisons will provide access via a flightpath to Ashran, while a Level 3 Garrison will provide a direct portal. To the best of my knoweldge, this flightpath is unlocked as part of a level 91 quest. Alternatively, you may visit someone else’s Level 3 Garrison and use it’s portal to Ashran.