In Stormheim, in the northeast corner of the map, there is a WQ called The Soultakers (up for 3 more days).
They are inside a cave, at the end of a hallway. Kill them to get a hidden artifact appearance for frost.
You will need a group, all 3 agro at once and have around 400 million HP each, and they daze often.
Just go to the location then search in custom group finder for a Soultaker group. It took me all of 5 minutes to get this done.