The Romulan legend of a final day on which demons will be loosed to destroy all life, which the Zhat Vash read as a prophecy about synthetic beings.
Ganmadan is an ancient Romulan story of the end of the world. It tells of a day when the shackled demons will break their chains and answer the call of the Destroyer, a figure named Seb-Cheneb, whose coming brings the death of all living things.
The myth runs through the first season of Star Trek: Picard. The Zhat Vash believe that it is a folk memory of a warning left by a vanished civilisation, the Admonition, and that the Destroyer is an artificial being. Narissa calls Soji by the Destroyer's name, and Narek cannot shake the belief even as he grows close to her.
Narek recounts the legend in full to Raffi and Rios in the season finale, Et in Arcadia Ego, as they work together to stop the synthetics of Coppelius from summoning a far greater machine intelligence.