OK I solved the ritual riddle and got the first symbol. Are the other two in the Temple Ruins Dungeon or somewhere else?? I assume you need those to get through the last door.

Thanks

Yes.
Spoiler:



You'll get one from the ghosts in the tomb area after you past the lava pit, provided you have the chewed up bones of the baby. And the other piece is in a corner of the room with a shadow (after the Indiana Jones puzzle).