To find the first clue you will have to eliminate a member of the Hunta order that you will find as soon as you build the headquarters of the Hidden Ones in Ravensthorpe. As soon as you eliminate it, you will find the first clue.
Hunta is in the town of Ledecestre in Ledecestreshire, north of Ravensthorpe, amongst the town's vendors.
And there is a second clue which is in Thieves' Warren which is in the middle of Glowecestrescire, at the top of the big hill, you can take a tunnel to get to the house where the clue is and the clue will be revealed to you on a table in the room.
When you have both tracks, you can find The Vellum in Glowecestre, near the docks.
After you have read this article on where to find the tracks for The Vellum in Assassin's Creed Valhalla you can find the two tracks and get this member of the order.
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