This page contains information regarding Star Trek: Picard, and thus may contain spoilers.
Aia, the Grief World, was a desolate planet located in the middle of the Eightfold Stars, an octonary star system created some 200,000 to 300,000 years ago by a synthetic species. That civilization had utterly wiped out their creators, after the latter turned on them. Before leaving to another dimension, the synthetics left behind a repository of memories meant for future synthetic species, promising that if summoned by artificial lifeforms, the synthetic civilization would return to protect them, by way of wiping out all known biological life forms in the universe, as they had concluded that organic species will inevitably turn on synthetic species and try to destroy them.
Hundred of years before the 24th century, a group of Romulans discovered Aia while investigating the Eightfold Stars. They experienced the memory reposititory, but because it was intended for synthetic minds, not organic minds, they experienced it as a dizzying array of horrific images and scenes of mass devastation, incorrectly interpreting it as a warning left behind by the ancient organic race against the creation of synthetic life, a warning that if artificial lifeforms were created, they would inevitably summon the "Destroyers" who had annihilated their civilization. Naming this "warning" the Admonition, they formed the Zhat Vash, a secret society dedicated to eliminating synthetics anywhere in the universe they emerged. Subsequent generations of Zhat Vash continued to visit Aia and submit themselves to Admonition, even though the process drove the majority of organics who experienced it irreparably insane. One such group in 2385 was led by Oh, and included Ramdha and "Narissa Rizzo". (PIC: "Broken Pieces")