The Festum are an eldritch-like spacefaring silicon superorganism and a cosmic horror element in the fictional universe of the Fafner in the Azure manga and anime.
The origins of the Festum is a mystery, but they have been present on Earth for millions of years. Being responsible for the evolution of humans from apes. Festum have a single agenda, which is to spread the benefit of assimilation to all sentient life throughout the universe. It's a silicon-based lifeform, a superorganism.
A hive mind known as the Mir is at the core of the Festum. All of the Festum are extensions of the Mir, and if the Mir is shattered its fragments become Mir and establish their own hive minds. Such "newborn" fragments can be influenced by non-Festum. Compared to natural-born Festum there is greater variety among the "newborn".
They are a species with the ability to communicate telepathically for dozens of km. Whom are able to destroy matter and teleport via the creation of wormhole-like spheres. The higher-level Festum are also able to create energy shields that destroy any physical objects that come into contact with it.
The ancient Mir on Earth was discovered in Japan by a scientist on 2098 AD. With a decade and a half, Earth was invaded by the Festum in 2114 AD. Which started with the landing of a 2nd Mir in the Arctic. In the initial invasion, the Festum took out every satellite, devastated the world's infrastucture, and assaulted every nation. By 2015, NATO was no more and the UN HQ had been destroyed. In the following year, the world discovers that the Festum had made the inhabitants of Japan sterile and fearing its spread, they nukes the archipelago. The only parts of Japan that survived was half of Hokkaido and the island of Okinawa. By 2010, the war had become a 3-way conflict between the Festum, the Neo-UN's Human Army, and the people of the island of Tatsumiyajima (the ALVIS). It was a war that continued for decades, though by 2151, the ALVIS humans had been successful in persuading the least aggresive of the two Mir to end hostilities and live in peaceful coexistence with man. By this time, the Neo-UN forces had been mostly wied out. They put the genocidal MIR into hibernation and prepared to head out to the stars to convince the Space Festum to likewise live in peaceful coexistence with mankind.