This page contains information regarding Star Trek: Picard, and thus may contain spoilers.
Seb-Cheneb, also known as the Destroyer, was a character in the story of Ganmadan, or the "Day of Annihilation". Described as a khalagu ("demon"), she was the twin sister of Seb-Natan. Seb-Cheneb was said by Romulans to be the "end of all".
After the death of her sister, Seb-Cheneb blew the horn of the hellbeast Ganmadan, summoning the ch'khalagu ("very bad demons") who would bring about the Thousand Days of Pain, in which worlds were burn and lives were lost. (PIC: "The End is the Beginning", "Absolute Candor", "Et in Arcadia Ego, Part 2")
In 2399, the Romulan xB Ramdha accused Soji Asha of being Seb-Cheneb, after seeing the sisters depicted on the final pixmit card in her hand. Ramdha subsequently became hysterical and pulled a disruptor on Asha before attempting suicide.