I came upon Labyrinthian, and there is a small circular area outside of it called Bromjunaar Sanctuary where there is a skeleton, a note about a magic mask, and the mask itself. If you put the mask on you are transported to what looks like an earlier time when nothing was yet ruins, the area is pristine. You can't, however, leave Bromjunaar Sanctuary. There is a shrine of what looks like 8 monk busts, but when you go to them you get "You Lack The Required Item." The only way to leave is remove the wooden mask, and then you are back in the present day ruins.
Has anyone seen this and know what needs done?