In Assassin’s Creed Valhalla you will find a quest as past of the main story called “Tilting the balance”. This quest will have no quest marker telling you where to go, instead you must follow some clues to locate a crypt where the king is hiding out. If you are stuck this guide will show you where to find it.
The main clue is the river names, the crypt can be found where the Awry and the Alne rivers meet. If you look around the map, you will find the rivers. If not, the map below will show you where it is.
The Old crypt south of Ledecestrescire
The crypt you find in the map location above is locked and you will be unable to get inside. This is actually the shortcut you use to exit the crypt once you have located king burgred.
Once you find this crypt, a quest marker will appear and if you walk over the hill to it, you will find a threaded camp with several crypt entrances. Any of these will lead you to the quest objective.