From Halopedia, the Halo wiki
Adjutant Revendicate was created from the mind of the Auditor in a series of events they would later describe as "a long story, and one that need not be told now", and assigned as one of the sub-monitors of Installation 07. Some time following the The Harbinger's defeat on the ring in May 2560, Revendicate would go on to contact Invariant Bias - the Contender-class artificial intelligence charged with caretaking the Absolute Record. Revendicate would not request to withdraw information from the record, but rather to deposit information into the archives gathered from various sources - fearing that the Harbinger's plan to bring about the return of the Xalanyn may come to fruition.
Revendicate's information was ultimately reviewed and accepted into the Absolute Record, with the two ancillae agreeing that the strength of John-117 may be the only thing capable of saving the galaxy from the Endless threat.
Adjutant Revendicate's information is an in-universe framing for the release of the Halo Encyclopedia (2022 edition).