The Mysteron Lunar Complex was a base constructed by the Mysterons inside Crater 101 on the moon. It was meant to serve as a new base or outpost but was ultimately destroyed thanks to the efforts of Captain Scarlet.
In the episode Lunarville 7, Captains Scarlet, Blue and Lieutenant Green travel to the moon in order to investigate Lunarville 7, whose Commander has declared that all human colonies established on the moon are now an independant government from Earth. In truth, the Mysterons have killed and reconstructed the commander so as to construct their new complex unhindered. Once the Spectrum agents discover its existence, they retreat back to Lunarville 7 and escape in a rocket as the Commander destroys the base.
By the time of the episode Crater 101, the mysteron complex has been completed and is fully operational. Captain Scarlet, Blue and Lieutenant Green are again dispatched to the moon on a mission to permanently destroy the complex by removing its power supply to prevent the Mysterons from reconstructing it.
Once they arrive in Lunarville 6, they are dispatched to infiltrate the complex while an agent named Frazer must plant a low yield nuclear bomb designed to wipe out the complex. Unknown to them, Fraser has been killed and copied by the Mysterons who plan to detonate the bomb earlier than planned in order to kill Scarlet, Blue and Green.
During the mission, the agents must square off against the complex’s defenses, which include massive alien vehicles that patrol the outside and hypnotic lights inside the complex. They eventually locate the power source, a pulsating crystal.
Having discovered Fraser’s treachery, Lunarville 6 send a rocket to warn Scarlet of the danger, which proves successful. While Captain Blue and Lieutenant Green evacuate, Scarlet succeeds in removing the crystal and fleeing just as the bomb blows up the complex.