MAP18: Optional Bases Opposed (BTSX-E2)

MAP18: Optional Bases Opposed is the eighteenth map of the second episode of Back to Saturn X. It was designed by Paul DeBruyne (skillsaw) and uses the music track "Birdsong," composed by Stuart Rynn (stewboy).

Official

 * 1) Southwest from the start, near a pool of slime with two dead marines and the chainsaw, there is a ring-shaped structure where a soulsphere is visible in the center (sector 562) through a small window. Press on the nearby green torch to lower a wall leading to it.
 * 2) At the north-eastearn part of the map is an elevated section of the level, where a soulsphere is visible on a pedestal. Near the stairs to that section is a square shutter. Press on it to open a small compartment (sector 96) containing a berserk pack.
 * 3) Ascend the stairs from secret #2 to find the soulsphere with a computer nearby. Press on the computer screen to lower the pedestal (sector 140), allowing access to the soulsphere.
 * 4) On the north-central part of the map, a button can be pressed to lower a rocket launcher, and which also lowers some walls containing monsters. On one of the monster closets that opens next to the rocket launcher, there is a hidden switch with the image of a crucifix. Shoot that switch to reveal a teleporter on another of the monster closets nearby, allowing you to telefrag two arch-viles in the beginning area and eventually access a fenced off courtyard (sector 787) guarded by two arch-viles (on Ultra-Violence and higher), containing a soul sphere, shotgun shells and armor bonuses.
 * 5) On the easternmost part of the map, shortly before finishing the path that ultimately leads to the red key, there is a desert-like area surrounded by blue torches where you are ambushed by teleporting monsters. You can use three small pilars on that area to climb to a small section containing a tiny hole. Falling down that hole leads to a small underground secret area (sector 509) containing a soulsphere, two boxes of rockets, and a medikit.

Non-official
On the western part of the map, at the start of the route leading to the blue key, there is a section with a zig-zag shaped path which ultimately lowers to reveal two arch-viles and a button unlocking a plasma gun and allowing to proceed further down the path. That same button also opens the bars to another section to the west which requires either the red of the yellow key and contains a BFG9000.

Current records
The records for the map at the Doom Speed Demo Archive are:

The (absence of) data was last verified in its entirety on February 21, 2022.

Player spawns
This level contains seven spawn points:
 * 1) facing north-east. (thing 35)
 * 2) facing north-east. (thing 570)
 * 3) facing west. (thing 571)
 * 4) facing south. (thing 572)
 * 5) facing north. (thing 573)
 * 6) facing west. (thing 574)
 * 7) facing east. (thing 575)

Things
This level contains the following numbers of things per skill level: