Malignant Information

A requirement for the appearance of the Tatari. Shared common knowledge circulating throughout a closed community.
Develops by making use of things like anonymous accusations, improbable testimonies, and popular trends. It will take on various forms depending on the circumstances, but at its core is “nothing.” It is for this very reason that the Tatari itself is said to have no true identity.
The “Bad News” used by the Night of Wallachia and the “Terror News” used by Vampire Sion were both forms of this, materialized with magical energy. The creation and control of malignant copies is a particularly advanced application.

Translator’s Notes
  1. ^ Also known as Malicious Information.
MB Act Cadenza PS2 Manual: Tsukihime Dictionary

Just as there are curses in real life, curses, known as “malicious information,” also exist in the Photonic Abyss that is SE.RA.PH.
This malicious information is comprised of negative thoughts and sentiments born from the actions of sentient beings.
Proclamations of evil. Self-serving lies, compounding upon themselves endlessly. Demagoguery that leverages straw men to enslave the masses. All of these forms of negative information are cancers that afflict the entirety of a community by corrupting that which is positive: the truth.
In the material world, this negativity would eventually fade away per its transient nature, but in SE.RA.PH., a world made entirely of data, malicious information is a foulness that erodes its territories.
All of the malicious information that has been recorded since humanity created a language-based culture is disposed of on the Far Side of the Moon. At first, only “useless information” was thrown away there, but once billions of pieces of malicious information accumulated, the mass began to manifest as a sludge that bled into reality.
The idealized, clean history of human society is recorded on the Near Side of the Moon, while the dreadful history of humanity’s terrible crimes is recorded on the Far Side of the Moon.
For virtual beings, who subsist on spiritrons, malicious information could be considered “junk food,” complete with the accompanying rush.
In the past, a certain Al planned to consume this massive amount of energy and control the Moon Cell, but it gave up on its plan in the final stages. It is said to have sunk into the depths of the Far Side of the Moon.

Fate/EXTELLA material: Encyclopedia of Fate EXTELLA