The Royal Palace is a location in the north-east of the Far Cry 6 Pagan Min Control DLC. When going there during free-roam you may find it locked and a voice telling you that you are not yet worthy. This guide explains how to access the Royal Palace.
To enter the Royal Palace you must have found all 3 Mask Pieces.
3 Mask Locations
Collecting the 3 Masks is the “main objective” of the Pagan DLC. The first is in the lake in the middle of the map, the second in the north-west corner along the yellow path, the third in the south-east corner along the yellow path. When you go near them they will be marked by an orange skull icon on the map, labeled as “Memory” locations.
Here are all 3 required Mask Locations (circled red):
After obtaining all 3 Masks you must bring them to the Royal Palace Gate (circled yellow in image above). Each mask will spawn a yellow orb that will fly towards the gate to unlock it.
This is basically the endgame area where the final fight takes place.