The portal from Dornogal to the Undermine is located at coordinates: /way 52.34, 50.71.

Note:

To activate the portal, you must complete the introductory quests from the World of Warcraft: The War Within campaign (patch 11.1).

Click the link to learn how to start the campaign: Unlocking Access to the Undermine.

How to get to the Undermine:

Simply follow the campaign quests, and you will automatically reach the point where you can activate the portal. First, the portal from the Undermine to Dornogal will open, followed by the reverse portal — from Dornogal to the Undermine.