Whoa. Where is that, how did you get them?
I only have Nahkrin and one other, I think it's a blue one.
In Labyrinthian, near the center is a circular building. In the middle is a skeleton with a note and a wooden mask. If you put on the wooden mask you go there.
There is also another door that leads to a maze, which isn't really a maze, but at the other end is a Word Wall.