But like, how do I get there? I have zero sense of direction.
Go up, up, right, up some stairs and continue until you find some stairs leading back down than go left, down, right. You'll be in the room with the mirror where you'll need level 4 mystic, than you'll lose Rinny. So after that go left, up, left and you'll see three, coffins open the middle one and get pulled in.