Realms of the Haunting

I just started chapter 13 Sword of the Dragon and I'm supposed to go to the mantel stone and teleport back to the tower but the game won't let me,it keeps saying something about a mask.I've tried all the masks in my inventory and looked at the WT to see if I was missing something but it looks like I've done everything I was supposed to.
Does anyone have any ideas?

ozma

It may just be a matter of using it properly. Double-click on one of the masks to use it.

Be sure to take the 2 potions from inside the painting.