The three UFOs were first seen in the midst of a near-global kaiju attack. Flying across the globe, Alpha, Beta and Gamma captured the Kaiju and seemingly removed them from the face of the Earth. The UFOs then traveled to their Mothership, docking onto it like the thorns on the base of a thistle. After the invasion plans were discovered by the Earth's military, the UFOs flew out to varied areas of the globe, transporting the monsters Zilla to Sydney, Kumonga to New Guinea, and Kamacuras to the Japanese Countryside. After Godzilla defeated the three monsters, all three of the UFOs regrouped above the foothills of Mount Fuji, and deployed Rodan, King Caesar and Anguirus. After Godzilla defeated (yet spared) the trio of controlled Kaiju, the UFOs flew back to Tokyo, where they docked with their Mothership again.
Ultimately, the ships were destroyed after the Mothership self-destructed.
- The Xilien UFOs are able to fly.
- The three ships can use a tractor beam which teleports objects away from the craft, or teleport them to the UFO's current location.
- Xilien UFOs also appear in Invasion of Astro-Monster, but they appear as fighter spacecraft rather than transport ships.
- The Xilien Transporters resemble large versions of the Xilien Fighters.