You wake up in a Tomb. As you wake up, you hear the announcer describe you as a new arrival and that a few others have arrived previously.
The exit is directly behind you, behind a sealed door. Ahead is a large chamber, to the right is a raised bridge, and the left is a room with a broken ladder.
Opening the door
You will first need to open the door leading to the exit. First, enter the left room, and try to move blocks to the ladder. The first block should be intact. Since that block is too large to climb, you need to use a smashed block as a stepping stone. Climb the blocks, and jump to grab the ladder. In some cases, you may grab the ladder with only the smashed block, but that is more difficult.
At the top, you can find a book with some narration from Eloff, another person who was stranded in the world. You will also see an obelisk, with spinning sections. Match the design on the front with what's shown on the nearby wall to activate the obelisk. It will then create a green beam that permits the exit door to open.
Lowering the bridge
You now need to get the portal key. It is located across the raised bridge.
Find two stone blocks, and push them into the large cage. If you somehow miss, the stones will be dropped in the large chamber and shatter as they hit the ground. Once you receive a message saying there's enough weight, find a third block and place it on one of the two pressure plates, and stand on the other one. It is possible to continue filling the basket, but it serves no beyond making the level unwinnable.
Once the bridge lowers, allowing you to get the portal key. You may now exit the level, or search for the artefact.
The strange artefact on this stage is hidden, being placed on top of a scaffold within the large chamber.
To reach it, move a block to the side of the scaffold, and use pieces of a smashed block to create a climbable pile. If you need a smashed block, you can either use the machine near the obelisk, or by pushing block off the side of the bridge (which will appear at the far end of the room). If you ran out of blocks, you can retrieve more from the far end of the room, by first placing a large block in the lowered section, and by placing a second large block on top.
With the artefact claimed, there's nothing else to do. Head to the portal and you'll be brought to the Resedential section.