To fully understand the role the Admonition has played in Star Trek: Picard, it is necessary to go back to its creation around 200,000 to 300,000 years before the events of the series. At that time, Episode 8 revealed, there was a point when synthetic life evolved to the point where there was some sort of cataclysmic event that led to much of organic life being destroyed.
Though the episode did not reveal what actually happened, it was sufficiently dangerous that the organic survivors decided they needed to leave a warning for future generations to stop it from happening again.
They brought together eight suns around a planet known as Aia or “The Grief World,” and put a machine on the planet. This machine was a memory bank/archive detailing exactly what happened when the synthetics threatened the existence of the organics, and was supposed to act as a warning to future civilizations against synthetic life.
Cut forward thousands of years into the future (but still centuries before the events of Star Trek: Picard), when a group of Romulan women rediscovered this eight-star system and the planet of Aia. Arriving on The Grief World, they used the machine and learned of the events of millennia ago. Though viewers of the CBS series did not get to see what these women saw, it was enough to drive many of those who saw it insane, and put many others on a lifetime quest to stop synthetic life from becoming too powerful ever again. These women formed the Zhat Vash, and called this machine the Admonition, a word that means “a firm warning” according to the Oxford English Dictionary.
The Admonition then became a secret kept by the Zhat Vash. They removed all details of Aia and its eight suns from star charts, whilst turning the machine into a sort of pilgrimage or ritual for members of their sect, who would visit the machine and learn about the horrific history contained therein. Many of these women, like the first women who rediscovered the Admonition, could not cope with the information and lost their minds, but those who survived it were given a life’s purpose.
These women then started to create anti-synthetic sentiment among the Romulans, as well as trying to prevent the emergence of artificial life technology on other worlds.
In the year 2385, they finally achieved one of their aims: A complete banning of all synthetic life in the Alpha Quadrant by causing a violent synthetic uprising on Mars. It is this ban that caused Jean-Luc Picard (played by Patrick Stewart) to quit the Starfleet and retire, which is where viewers found him at the start of the show.
