There is a way you can get through the barrier without having the amulet:
1. Step near the barrier.
2. Use telekinesis to grab a jar from beyond the barrier and move it right next to the barrier.
3. Open the jar through the barrier (that seems to be a bug, should not be possible I guess)
4. Put one of your pyramids into it.
5. Then move the pyramid out of the jar to the ground behind the barrier.
6. Teleport to the pyramid using your other one.
