Simply, follow the road within the First champer, then go to a loading spot, and then you will see the first gem, after that you will find a tomb, and fall on that that will lead you, to a place with a lot of parts for skelets, follow that way, you will meant leanna (If you chosed to save Leanna, and banished Xana) If you follow that road you will get to a huge room, with a large tomb within a wall (Secret area) with Staff of Fire (I think). Then a Lich will appear, after you have killed him, you find a Gem, within the tomb, and after that you will need to go behind the tomb and crawl up a chain, that will lead you to a load point, and after that, you will get to the place behind the closed door, that you can't get to, becouse the switch is at the other side, then jump down to the bottom AND hit the water, and then you will find a small Isle of dirt, with a tomb, then you will find the chest there, and then make you'r way to the top, open the door, hit up to the Spider Statue, then you will enter the Godess room, to get the Skull of Shadows, but you need to kill spiders.
I hoped this helped you.