|“||Your mission is to search the underground tomb where the transfer device is hidden. Once you've located it, destroy the device!||„|
The underground tomb, also referred to as the catacombs, is an ancient location on Bion, most likely constructed by the ancient Bion race. It is the setting of M20: Insurrection in Metroid Prime: Federation Force. Who or what is encased in this tomb is not made clear during the mission.
Following the destruction of the Excelcion Transfer Device, another was discovered on Bion within this tomb. Upon entry to a cave, the Federation Force finds the Transfer Device, but is ambushed by the Space Pirates, who use an electrical surge from the device to separate the Marines from their Mechs. After this, they fall through the damaged ground into the ruins below.
The first chamber of the underground tomb is a winding maze containing Thermo Spheres that encircle the tunnels, and pits of lava. The Marines carefully navigate the maze and reach the center, which contains a pressure pad (all of the rooms are connected by a pressure pad door). Upon using it, the Marines are dropped further down into a damaged chamber with perpetually falling boulders, a dedicated terminal and the lead Marine's Mech. In multiplayer sessions, the other Mechs are found elsewhere in the mission, making it much more dangerous. However, remaining suitless allows the soldiers to access a number of MODs in the tomb, which are inaccessible with their Mechs.
The Marines make it past the boulders to a batch of rubble covering the exit. In the next chamber, a series of bridges and platforms, the Marines are accosted by Flying Pirates. At the end of this chamber is a bridge suspended above lava, with a switch that must be shot repeatedly to lower the bridge. Through here is a corridor lined with lava falls, which leads into an outdoor corridor with rising and falling Thermo Spheres, and Fire Hoppers. After the lava portion is a longer corridor filled with Pirate Troopers, which leads to a small room with crates that may contain AUX ammo. This comes out to a room that is half suspended above lava, and half dry land.
On the latter half, the Marines do battle with a number of Elite Pirates and a Collosun, before finally gaining entry to the Transfer Device's room. While damaging the nodes on the Transfer Device, the Marines are forced to deal with an endless stream of Troopers seeking to stop them. However, the Force is ultimately able to destroy the Transfer Device, and leaves the tomb.
- MOD 1
- Close to one of the lava pits near the entrance to the maze.
- MOD 2
- In a small tunnel behind the lead Marine's Mech.
- MOD 3
- Requires suitless Marine. In the large area with Flying Pirates, this MOD is located on the other side of a small hole.
- MOD 4
- Requires suitless Marine. In the same area, this MOD is in the same part of the room, reachable by walking up a tilted pillar.
- MOD 5
- Requires Freeze Shot. Behind a lava wall after the Fire Hopper and Termo Sphere chamber.
- MOD 6
- Requires suitless Marine. Above the entrance to the above area
- MOD 7
- In the chamber with the crates, there is another lava wall on the right side; beside a small tunnel.