Alien Pass
From Timebomb Madness Wiki
Overview

Alien Pass is a map debuted on release.
Alien Pass is a hilly map with 2 giant mountains next to eachother with a gap inbetween. Usually, survivors make a bridge to cross the 2 mountains, and that's usually where most bases are built on Alien Pass.
There is also a dark cave at the bottom of the map with 2 entrances on the large variant of this map. This map was included when the game was created, being one of the 3 maps that were in the release.
The map is based off Homestuck's "Alternia", having the exact same moons, trees, and color schemes. This would fit the map's name, as in it's source material, Alternia is the alien planet of the "Trolls".