We X-Nauts aren't all rainbows and lollipops. I could assure you, we could be quite nasty.
~ Sir Grodus
The Secret Society of X-Nauts or the SSOX, is an organization of creatures believed to be aliens that are trying to take over the world, and serve as the primary antagonistic faction of Paper Mario: The Thousand-Year Door. They are led by their leader, Sir Grodus, who is trying to rule the world and make it a perfect world based upon him.
They fall apart at the end of the game, with only six members remaining.
The X-Nauts can create machines, make potions to hurt their enemies which have different effects like decreasing Mario and his partner's defense and size, and set them on fire, much more just to get closer to their goal. They are also able to make potions to improve their abilities in battle such as making themselves invisible, increasing their power and increasing their agility. They also count with their biggest creation, the Magnus Von Grapple which was first seen during the Chapter 3 where Lord Crump tried to get rid of Mario and his friends along with the Punis. After Magnus got destroyed, the X-Nauts PhD created a second robot with more improvements which was again used by Lord Crump in Chapter 7 called "Magnus Von Grapple 2.0". The X-Nauts also count with TEC-XX, a super computer created by Sir Grodus to be a perfect computer and help him in his plans. However, when he developed feelings towards Princess Peach throughout the game, he decided to help her to escape from the X-Naut Fortress at the end of Chapter 6 until a X-Naut told everything about TEC helping Princess Peach to Sir Grodus and ordered to shut down TEC for his betrayal.
When Mario and his party went to the moon to rescue Princess Peach and steal the Crystal Star from the X-Naut Fortress, they realized that Princess Peach wasn't anymore in the moon since Sir Grodus learned about TEC helping her and took her to The Thousand-Year Door. Lord Crump is the final boss of this chapter, this time using a new and improved Magnus Von Grapple called "Magnus Von Grapple 2.0". However, once again Magnus Von Grapple got destroyed and while Lord Crump was sent to the space, the X-Naut Fortress got destroyed with all the members in while Mario and his party escaped thanks to TEC-XX who gave his last desire in helping Mario in the Teleporter to return to Rogueport.