|First appearance||Paper Mario: The Thousand-Year Door (2004)|
|Greater location||The Moon|
|Inhabitants||X-Nauts, X-Naut PhDs, Elite X-Nauts, Z-Yux|
The X-Naut Fortress is Sir Grodus' main base of operations which is located on the moon and the home to the X-Nauts in Paper Mario: The Thousand-Year Door. Princess Peach is also taken to here. The last Crystal Star, the Crystal Star, is held there and Mario and his friends have to use the cannon in Fahr Outpost to reach this place and fight Lord Crump (while controlling Magnus von Grapple 2.0) to get the star. Grodus travels between the earth and his fortress using a teleporter, which has one end located in his laboratories and the other end located in Rogueport Sewers. The base is also the home of TEC-XX, which is the main computer of the whole fortress. Also, after Mario gets the sixth Crystal Star, Grodus takes Princess Peach and leaves the fortress (possibly giving it to Lord Crump) so he can go to the Palace of Shadow. After Mario successfully destroys Magnus von Grapple 2.0, he gets the seventh Crystal Star. After that, the fortress explodes and Mario is unable to go back until the final boss is defeated.
The fortress is essentially a five-story building built deep under the moon. It is all connected by a series of hallways and two elevators. The deeper Mario or Peach go, the dimmer the lighting is.
When the player Spring Jumps into the air duct from the Yux lab on Sublevel 2 and uses Paper Mode to slip thought the vent on the far right, they land in a changing stall where Peach used to put on the X-Naut suit. If they pull the curtain back, Mario and his partners become 8-bit. This lasts until they leave the room.
- Elite X-Naut
- Magnus von Grapple 2.0 (Chapter 7 Boss)
- X-Naut PhD
|Blue Potion||In the lab on sublevel 2, it is on the desk for Princess Peach for use in Chapter 5.|
|Card Key||To the left of sublevel 2, it is guarded in a chest beyond the electrical floors.|
|To the left of sublevel 3, it is guarded in a chest beyond the electrical floors.|
|To the right of sublevel 2, it is on the computer desk in the back room of Sir Grodus's area.|
|To the right of sublevel 3, it is in the factory room. Accessible from the airplane panel near the right exit.|
|Cog||In the transportation room on sublevel 2, it is on top of the controller. Accessible from the air vent with Koops or Yoshi.|
|Crystal Star||Dropped after Magnus von Grapple 2.0 is defeated.|
|Data Disk||To the right of sublevel 2, it is on the shelf in the computer room behind Sir Grodus room, for Princess Peach to steal in Chapter 5.|
|Elevator Key||To the right of level 1, it is guarded in a chest beyond the electrical floors.|
|Won after the 66th Annual Quirk Quiz.|
|Feeling Fine||To the left of sublevel 1, it is on the item platform to be retrieved with the crane.|
|Feeling Fine P||To the left of sublevel 1, it is on the item platform to be retrieved with the crane.|
|Green Potion||In the lab on sublevel 2, it is on the desk for Princess Peach for use in Chapter 5.|
|HP Drain item||To the left of sublevel 3, it is in the question block on the south side.|
|Orange Potion||In the lab on sublevel 2, it is on the desk for Princess Peach for use in Chapter 5.|
|Red Potion||In the lab on sublevel 2, it is on the desk for Princess Peach for use in Chapter 5.|
|Sleepy Sheep||To the left of sublevel 2, it is in the yellow question block on the back side.|
|Star Piece||To the left of sublevel 1, it is on the item platform to be retrieved with the crane.|
|In the southwest corner of the air vent on Sublevel 2.|
|Super Shroom||To the right of level 1, it is in the yellow question block on the back side.|
|Ultra Shroom||To the right of sublevel 3, in the factory room, it is on the left high platform in the background.|
- "Who knew there's be such a weird building on the moon... It's kind of crazy, actually. I mean, it's got a big glass dome to keep all of the air from leaking out...What's that? Yeah, now that you mention it, I guess we were OK out there with no air to breathe...................................Yeah, I'd rather not think about that too much, I guess. Let's change the subject."
- "This is the X-Naut Fortress. This seems to be the only way in or out. The stars look really nice through these windows, but I guess now's not the time..."
- "This is a fortress corridor. An elevator connects it to the lower floors. I guess this fortress extends pretty far beneath the surface of the moon, huh? I mean, I hate Grodus, but I gotta give him some props for a pretty cool evil hideout."
- "This room looks like it was meant to store something... It's booby-trapped, I think. Not to totally change the subject or anything, but how's your memory, Mario? If you have trouble recalling the full path, you oughta leave and reenter."
- "This looks like a storage room for valuables. The crane can grab stuff up there. It should work if you set a gear in place and press those switches in order... I'm sure you can handle it. It's not exactly moon-rocket science here."
- "What's this room for, huh? I feel like I've seen that face somewhere before... Hmmm... Oh well, forget about it, I guess."
- "This room looks like it was meant to store something... It's booby-trapped, I think. If you wander off the correct path, it looks like you'll take damage, don'tcha think? Rooms like this ALWAYS have a hint, though. It's like, a law. See anything like that?"
- "This is Grodus's lab. He must have his researchers work on various potions here. I don't think we should touch any of this stuff, though... One wrong move and... KABOOOOOOOM! ...Know what I mean?"
- "This looks like some kinda teleporter. Who knows where that thing would send us! Maybe that's what the X-Nauts used to go between the moon and the earth. I think we have to switch it on and then stand on the platform to use it."
- "This looks like a lab for genetic experimentation...maybe Yux were made here. I guess they must have some pretty advanced technology if they can do stuff like that. Hey, by the way, Mario... You see up there? One of those ceiling panels is loose. Don't you have some super move or something that can get us up there?"
- "This is a changing room. I guess even X-Nauts have to change out of their uniforms... But what do they look like under those suits? I'm...not gonna think about it. There's a ventilation duct in the ceiling at one end... That's not good for privacy!"
- "This place is a bit overdone, huh? It just screams, 'Hey! I'm an evil mastermind!' I wonder if poor Princess Peach got dragged in here before?"
- "What's this room for, huh? Is it some kind of office for the X-Naut boss or what? Maybe we should give it a once-over to make sure we don't miss anything. Boy, and what's with these tanks full of Nibbles? Jeepers, that creeps me out."
- "This room looks like it was meant to store something... It's booby trapped, I think. If you stay on the tiles that were lit up, I think you'll be OK, Mario. Er... But you should totally go first, one way or the other..."
- "There are three panels here. I guess that means we need three Card Keys, huh? There must be something pretty important behind this door to have such security..."
- "This is the X-Naut factory. I think they make all kinds of stuff here. It's pretty complicated, what with the crane and the pipe, and all those gears... Maybe we should just take this room one bit at a time, don'tcha think?"
- "This is where they built Magnus Von Grapple and Magnus Von Grapple 2.0. But there doesn't seem to be anything here now... Nope. Let's go, Mario."
- "This is the computer room. This must be where Princess Peach met with TEC."
- "Wonder what this room's for? There are beds and lockers, but we can't nap here. There's nothing else, really. The weird thing is, it kind of smells nice in here, huh? Why do you think that is?"
- "This is a...shower room? I guess every evil-guy base of ultimate doom needs one... Just because you're evil doesn't mean you enjoy B.O., y'know what I mean?"
In-game map description
Names in other languages
Megabatten no Ajito
|X-Naut Base (Megabatten is the Japanese name of the X-Nauts)|
|French||Repaire Mégacruxis||X-Naut Lair (Mégacruxis is the French name of the X-Nauts)|
|Italian||Covo di Giustignardo||Sir Grodus' Lair|
|Spanish||Base de los Mega X||Base of the Mega X ("Mega X" is the Spanish version name of the X-Nauts).|
- A single Elite X-Naut hides in the shower room on Sublevel 4 while the fortress is active.
- During Princess Peach's Interlude after Chapter 5, TEC-XX asks Peach to drink an invisibility potion in order to secretly enter Sir Grodus' room and upload important data on a disk into the room's computer. When this happens, the computer screen shows the Famicom Disk System boot-up sequence which is then shortly followed up by an animation and some music from an unknown game.
- In the Japanese version, the "safe path" in X-Naut Fortress's third puzzle room is only two squares long as opposed to three squares long in the international versions.
- The password required to progress further into the area, 014029, can be alternately read as 『おいしー おにく』 Oishī Oniku in Japanese, which means "delicious meat". The password was changed to "excuse" in the French version for unknown reasons.