When you first enter the True Tomb, there is a portal to the southeast, take it.
Now you are in a small room, once again take the portal to the SE.
Now you are in a bigger room, keep going SE through this room and you will come to a portal, take it.
In this room there is a town portal orb to the SE.
Once you get to the room with the TP orb you don't need to take anymore portals, so don't take any.
You now want to start traveling south west.
If you stand at the Tp orb, walk west of it and you will come to a hallway that will lead you SW.
Go down this hallway and when you come to a path that will take you down, take it.
Follow this path SW until you hit the bottom corner of the map, you will encounter 1 or 2 fire turrets on this path.
Once you are in the corner Go northwest until you reach a well.
When you get to the well go northeast into this large room.
At the top right of the room is the next level.
GL