|Universe Based On||X-Com series|
|Level Designer||Lars Luron|
|Boss(es)||The Synomium Device|
|Introduced in Game Version||v0.5|
T'Leth is the first and only unlockable level in World 5, Gehenna. T'Leth is based primarily on the classic PC strategy game X-Com: Terror From the Deep, and includes numerous elements from the other two games in the X-Com series, X-Com: UFO Defense, and X-Com: Apocalypse. It is modeled after the various Alien Colony and Artefact Site missions from Terror From the Deep, and takes the player on a journey deep inside a massive alien colony at the bottom of Gehenna's ocean.
The level starts off out in the middle of the ocean, with nothing around apart from a few native enemies and an abandoned X-Com submarine. After a short swim, the entrance to the base comes into view. Inside, the player finds themselves inside a massive alien base, filled with bizarre organic technologies and hostile alien creatures. Fortunately, the various paths and corridors are strewn with various alien weaponry, along with small caches of Sonic Pulsar grenades, which will help the player to defend themselves. Being underwater, most rooms in the base are half submerged, often providing two separate routes through the larger areas; a dry upper route, providing standard gameplay, and a submerged lower route, filled with various aquatic creatures. Passage between the upper and lower routes is provided by strategically placed Levitator devices, which generate pillars of anti-gravity energy that function like elevators between floors.
Throughout the level are various message blocks with messages in the form of X-Com mission logs, detailing the ill-fated investigation of the base by a team of X-Com operatives, who discovered T'Leth during their investigation of the disappearances in the Bermuda Triangle. The logs describe the operatives' findings throughout the base, such as the aliens' activities, their plans involving Gehenna and Legion's Finest, and an unexpected connection between the Sectoids and the Villain Alliance member Mewtwo. Several of the more informative logs are stashed in out-of-the-way locations, however, requiring the player to do some exploration in order to uncover the entire story.
The two upper levels of the base are modeled after the interior of a standard undersea colony, and contain only basic enemies, such as Sectoids, Brainsuckers, Lobstermen, and Hyperworms. The second floor contains a few more dangerous enemies, such as Poppers and Half-Life Shock Troopers, and is noticeably darker than the upper floor. After that, the player finds themselves in a strangely moisture-free section of the base, which appears to be used for research of some sort. The area is modeled after an alien base from the first X-Com game, and contains no enemies other than Sectoids and Bio-Drones, although it is filled with strange stasis chambers containing various creatures and other organic materials from throughout MKF. At the end of this section, the player will find themselves confronted by a deadly Cyberdisk, which they will have to destroy using a limited amount of weaponry.
The explosion from the destroyed Cyberdisk causes the floor of the room to collapse, causing the player to drop into an acid-filled cavern below. This cavern is filled with a variety of peculiar alien plants, along with what appears to be a number of alien eggs. At the end of the cavern the player will find themselves trapped inside an alien hatchery, where a number of alien eggs, pods, and other aliens will continuously spawn in an attempt to devour the player. Once the player manages to defeat enough of the spawning enemies, the door will open to the next area.
The next and final area is the deepest part of the colony. There is very little available light down here, decreasing the player's visibility range, and there is much more water present than in the upper floors. This area is modeled after the inside of the Artefact Site missions from Terror From the Deep, and contains a multitude of enemies much more dangerous than the ones encountered above, such as Tentaculats, Multiworms, and Half-Life Ichthysaurs, along with some of the more powerful enemies from the upper floors, such as Bio-Drones and even a few free-roaming Cyberdisks. After managing to cross this area and descend through the central Levitator structure at the end, the player will reach the final checkpoint before the colony's main control room. Inside, the player will find the Synomium Device, the psionic energy generator that regulates the entire colony. The player will need to destroy it in order to shut down the colony for good, but it won't be a simple task. While the Synomium Device itself is nothing more than an inanimate object (it can't even harm the player in any way), it is heavily armored, and can only be damaged by the explosion of a Sonic Pulsar grenade, of which several are scattered around the room. On top of that, the colony's residents will not just sit idly by while the player destroys their base, and will constantly storm the room attempting to kill the player before they can succeed. After about 10 or so well-placed Sonic Pulsars, the Synomium Device will explode, permanently disabling the entire colony and putting an end to the aliens' grisly plans.