Melun Hoard Map
Blihaut is in the northeast of Melunois.
The Hoard Map is behind the waterfall, where the Norse Man is looking at.
The Oil Flask needed to open up the closed path behind the waterfall is in the locked room.
The key is underneath the wooden boxes next to the Norse Man.
Carry the Oil Flask to the destructable wall and put it down in front of it.
Now you can shoot it through the water.
The Hoard Map shows a drawing of the environment:
Blihaut in the bottom part and some ruins north of Blihaut with an "X" marking a spot.
North of Blihaut are unnamed ruins already in the Amienois Region.
The loot lies next to the ruins in the grass (second set of screenshots)
The Flying Paper starts at the west of Melun and ends at the same location.
So just let it fly away and stay in position, if you don't mind having a chasing break...
Reward: Ouroboros Scheme (Head)