I have only 1 mask left. The mask under the Phil (the Fish).
Does anyone know where to find it? I have searched every level.
Any help would be appreciated.

Thank you very much.
Now thats what the solution of the puzzle is for.

I just realized because of this topic that the fish mask is named after FEZ designer, Phil Fish.

Also I believe that the camel and monkey masks are named after Rami Ismail and Jan Willem Nijman of Vlambeer. And the bat mask is probably named after Nigel Lowrie of Devolver Digital.