Thaumopoleans were very advanced with their technology and lived a very long time. They saw men as destructive and decided to sink their city beneath the sea.
Lara Croft had found one key fragment of the armory of Thaumopolis, and several Thaumopolean Nesting Dolls, and started searching for the sunken city. She was approached by a living Thaumopolean Anton Cooper who possessed another piece of the key. They traveled to the sunken city via his submarine, where they found Liberty Project, lead by Mr. Madison. Madison had the rest of the key fragments, and made duplicates of the rest. However, without using the correct key the armory would explode and cause a massive tsunami. Lara opened the door with the correct assembled key, and the guardian sent Lara and Anton to dream chamber to see who is worthy of a prize. Lara emerged victorious and all she claimed was part of the Nesting Doll set. When they left, Anton Cooper blew up the entrance to the sunken city, and scattered the key fragments to the bottom of the sea.