DOS2:Threads of a Curse

Threads of a Curse is a quest in Divinity: Original Sin II. The quest is initiated upon picking up an Odd Skeleton Arm at   X: 360  Y: 80  .

Objectives

Find out what the skeletal arm wants.
We found a strange skeletal arm on the coast. It's waving to get our attention.

Discover where the skeletal arm is leading you.
After pulling the skeletal arm out of the sand, we found out it's missing a body. When on the ground, the arm points in a certain direction.

Look for a way to deactivate the barrier.
There's an ornate chest by the water, surrounded by a stone circle and a powerful barrier.

Speak to the skeleton with sartorial sense.
When the barrier dropped, a finely-dressed undead lunged out of the chest.

An arm sticking out of the sand can be found at   X: 360  Y: 80  . With a wits check, you will be able to pry the arm free.