The 'Sky Fortress Damocles' (天空要塞ダモクレス Tenkū Yōsai Damokuresu ) is a floating fortress developed by the Toromo Agency in Cambodia. It serves as the main base for Schneizel's splinter faction. Based on its schematics, it is powered by a series of solar cell generation systems, similar to those used in Tokyo's concession areas. Spanning three kilometres on its longest axis, it is armed with several F.L.E.I.J.A. warheads; however, it requires approximately ten minutes to reload after firing just one. It is also rendered nigh indestructible due to the Blaze Luminous shield that encompasses the entire fortress. Its only weakness lies in the fact that the Blaze Luminous has to be opened near the F.L.E.I.J.A launch tube in order to fire a F.L.E.I.J.A.
The Damocles was originally developed by the Toromo Agency in Cambodia at the request of Schneizel el Britannia. At the same time, Schneizel took custody of all remaining F.L.E.I.J.A. warheads and had them deployed to the flying fortress, Lelouch later noting that it was a perfect base for F.L.E.I.J.A. The fortress remained under construction for much of the second season, completed after Lelouch vi Britannia ascends to the throne of Britannia in 2018.
Damocles was first deployed to the Holy Britannian Empire, where it obliterated the imperial capital city, Pendragon, with a F.L.E.I.J.A. warhead that had its limiter removed, displaying the weapon's increased destructive yield as well as paralyzing the Britannian government. Schneizel's intended plan for the Fortress was to be as follows: within 10 days following the Pendragon attack, Damocles would enter the airspace of the United States of China. Then, it would ascend 300 kilometers above the surface. From there, it would attack every nation engaged in war, with a total of 23 intended targets. Schneizel's intention was that, by completing this plan, which would result in the deaths of an estimated 1-2 billion people, he'd bring about permanent peace through fear. The Damocles then steadily gained altitude in the days after the attack, and entered the airspace of Japan during the Battle of Mt. Fuji, where it used several F.L.E.I.J.A. warheads against Lelouch's forces. The Damocles continued ascending, moving over the Pacific Ocean on its predicted course. Unassailable due to its powerful Blaze Luminous, the Damocles remained unscathed during the battle.
After the completion of the F.L.E.I.J.A Eliminator during the battle, Lelouch vi Britannia, Suzaku Kururugi and several Britannian Knightmares used the weapon to cancel the detonation of one of the warheads before using the small window in the Damocles' shields to infiltrate the fortress. Inside the Blaze Luminous, Suzaku Kururugi dueled Gino Weinberg
and Kallen Kōzuki using the Lancelot Albion, with Suzaku finally being defeated and seemingly killed. Inside the fortress, Lelouch cornered Schniezel and defeated him by casting his Geass. He then confronted Nunnally vi Britannia and obtained the Damocles' main firing switch from her, ending the battle with victory for him and the Britannian Forces. He then declares himself the absolute and unopposed ruler of the world.
Emperor Lelouch, after the Battle of Mt. Fuji, placed Marrybell mel Britannia in charge of the fortress in his stead, and it is assumed that he used the Damocles to destroy and threaten any country which tried to oppose him. Prior to the plan to assassinate him, Nonette and the Glinda Knights, along with Peace Mark, planned an attack on the base.
After the assassination of Lelouch vi Britannia and Marrybell mel Britannia, the Damocles was destroyed by sending it to the Sun.
- Damocles is a fictional character from Greek mythology, a courtier of King Dionysius who was given the chance to see what it was like to be king for a day. But the king arranged to have a sword hanging above the throne by merely a horse hair, until Damocles begged to be allowed to step down, and he realized that with great power, comes also great danger.
- Thus the name of the fortress itself, which was supposed to usher an era of world peace and happiness, is an ironic play on what Lelouch and the others argued all along, that true peace and happiness cannot be brought about through tyrannical rule and the constant threat of space-borne weapons of mass destruction.
- In the crossover mecha turn-based strategy game Super Robot Wars Z2: Saisei-Hen (which features Code Geass' plot among many others), the battle to stop the Damocles can play out in two different ways, depending on the player's choices. In the "normal" route - in which the Black Knights betray Lelouch - it is actually Emperor Lelouch who controls the fortress. Ironically, it is only in the "If" route - an alternate story path where Lelouch stays with the Black Knights - where Schneizel controls Damocles. In both situations, the Damocles itself is considered an enemy unit, and can be attacked.