First of all, this might be a SPOILER for those who like treasure map games, i.e. want to find the buried treasures on their own.
This was quite fun, having good old adventure game vibes, thanks to devs.
There is a "protected chest" on the northernmost snowy area of Scosglen, which is very easy to see, drops the first scroll (1/4)
Since we don't have a Scosglen minimap, I took screenshots of the other 3 chest locations:
Chest 2/4: The scroll says it's in "farmlands", the chest is northwest of the central green area:
Chest 3/4: It says south of farmlands, in the "Praying Temple". Go right and down, you will see a fancy shrine area, the chest is hidden among the trees to the left:
Chest 4/4: Just left of the entrance portal to the area:
Transmuting these all 4 scrolls in the cube creates the design of Dulra Aegis charm design (Tenets to complete the charm drop from their corresponding corrupted druid)
Killing the beholder in the cemetery gives an "eye" ingredient. As of now, I have the 2.1 Dulra Aegis charm so I can't apply that ingredient (bugged or intended, doesn't matter), so what I think is that applying that ingredient will make it possible to open the portal to the Secheron's Destroyer dungeon, which I suspect to spawn in the arena in the northernmost point of the map. I would be happy if I get a confirmation on that.
Happy treasure hunting!