The Colony Ship T'leth was an alien vessel that crash-landed on Earth at the end of the Cretaceous Period, and serves the role of the final mission in X-Com: Terror from the Deep, like Cydonia had in UFO Defense.
Arrival in SolEdit
The Alien Colony Ship T'leth arrived in Sol millions of years ago, during the late Cretaceous. A solar flare had caused the ship's navigation systems to malfunction, bringing it on a collision course with Cretaceous Earth. The wounded T'leth broke through the clouds in a huge fireball, crashing into the seas with the force of several hydrogen bombs. The impact of the massive Alien vessel wiped out a large portion of the young world's life, bringing an abrupt end to the Cretaceous Period. The Alien passengers were kept in stasis for many, many years, while other ancient aquatic species (including an aquatic offshoot of humanity) were harvested for their own purposes. The ship had sunken to the bottom of the ocean, coming to rest in a deep trench in what would eventually be the Gulf of Mexico, waiting for a sign...
Millions of years later, after the events of the First Alien War, X-Com has retired after saving the Earth from the Alien invasion. However, they did not count on the calculating Martian army having a contingency plan. After the heroic X-Com soldiers left the forsaken Cydonian base, a tachyon bolt blasted from the ruins, hurtling through space until it reaches its target: Earth. The beam strikes an ancient comm-receptor that belonged to the shipwrecked T'leth. The signal was recognized by the computer, which had slowly started to awaken the sleeping aliens.
The Second Alien WarEdit
In the year 2041, the Aliens have now begun their attack on Humanity, harvesting resources from the seabed and striking sea-based targets with powerful flying subs. Against these overwhelming odds, Humanity has brought the X-Com back into action to combat the Alien threat. After battling their armies, most of which were ancient terran species (including their forebears the Gillmen), and destroying the Synomium Devices that powered their Molecular Control web, they had finally acquired the location of T'leth and the means to get there by way of the advanced transport sub Leviathan. Mustering up their forces, the best and brightest X-Com soldiers stormed the Alien fortress.
The Ultimate EnemyEdit
After breaching the nigh-invincible Alien defenses, the X-Com assault team found an area deep within the wrecked colony ship that spiraled downward, which the Aliens had guarded fiercely for some reason. After reaching the final level, they had reached the reanimation chamber of Alien controller, a tentacled Cthulu-like monster called the Alien Horror, very much like the Alien Brain on Cydonia. Its destruction caused the remains of T'leth to self-destruct. The X-Com soldiers did not escape, but the last of the Aliens were eradicated. The destruction of the colony ship caused a drastic change in the world's environment, which would effect the world as we know it in X-Com: Apocalypse .