the Safe requires "S.O.U.L" of 4 Animal Guardian.
And I think related Mosaics are as followed.
0-Scorpion (At the Middle-room of the Guest House)
4-Owl (At the Underground of Building that has the Safe)
5-Unicorn (At the Stable on the North of the Court Yard)
1-Lion? (At the Middle of Main Ballroom.)
(the Shadow of Chandelier ovrelaped with Mosaic, so I am not sure exactly which Animal the Mosaic is.)