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 lies or conflicts. To initiate the system, his plan originally called for merely one immortal Geass Code. However, Marianne stated that after further research of Geass, it was discovered that in order for the system to have a 100% effectiveness, it required two Codes. As Charles was about to merge his Code (which he had taken from V.V.) 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.
Akasha (आकाश, Aakash) is a Sanskrit word literally translating to sky or indirectly meaning "aether" ,space as in space-time and rarely heaven.