Sword of Akasha

The Sword of Akasha is a large and mysterious hovering temple-like structure. It is unknown as to how it was created, but it was discovered by the Holy Britannian Empire and used almost exclusively by the Emperor himself. It has been said that its purpose is to kill the gods as per the Emperor's Geass contract with V.V.. Its design resembles a combination of ancient Roman and Celtic architecture. However, this is revealed to be only the platform. The Sword of Akasha is actually a large megastructure resembling a Dyson Sphere that encompasses the temple.

The system is located in the World of C. It is commonly depicted as floating in billowing clouds with no land or sky in sight. This is revealed to be merely an illusion that hides the actual structure itself. Entry to the temple seems only possible using Thought Elevators. It also seems unusually close to a Jovian planetoid (presumably Jupiter) that embodies the Gods. The temple was greatly damaged by Lelouch using the Shinkirō's hadron blasters in his attempt to rescue C.C.. When revisited by Charles, most if not all the architecture on the highest platform were destroyed.

Charles attempted to use the system to initiate Ragnarök, which would destroy the gods and reunite all humans, both living and dead, as a single will; believing that it would create a gentle and better world without conflicts. To initiate the system, he originally required merely one Code. However, after further research of Geass, he discovered that in order for the system to have a 100% effectiveness, it required two codes. As Charles was about to merge his Code with C.C.'s, Lelouch defied his parents by stating that the world they sought to create would be stagnant, and that "forcing good intentions on other people is no different from an evil act." He uses his Geass to influence the Gods to continue the progression of time, in effect causing his parents to be absorbed by C's World. As a result of this, the Sword of Akasha is presumably no longer operational.

Terminology
Akasha (आकाश, Aakash) is a Sanskrit word meaning "aether", also meaning space as in space-time and rarely heaven.

Trivia

 * https://en.wikipedia.org/wiki/Akashic_records
 * The word "Akasha" also appeared in another anime/visual novel series, Fate. In Fate, the Akasha (also knows as The Root) is the is a metaphysical location within the Nasuverse as the "force" that exists at the top of all theories on dimensions. It is the location of the Akashic Records, the Swirl of the Root (根源の渦, Kongen no Uzu?), which is the source of all events and phenomena in the universe.
 * In the anime/manga Mirai Nikki, there is a place in Deus ex Machina's world called the Akashic Records which holds all the collective intelligence of mankind. This is similar to Akasha in Code Geass, however the records do not survive in the previously mentioned if the god(s) should die.