In Assassin's Creed Valhalla: Wrath of the Druids, you can come across the Ui Neill Artifact, one of the collectible items. On this page of our guide, you will learn where to find masks and how to reach them. This will make it easier for you to max out the Dublin region.
You will find the mask to the north, just above the sync point.
To get to the mask, you must destroy the obstacles blocking the passage. You will do this with the right arrows or jugs of oil.
Once inside, approach the wall, and you will see the artifact.