Saeena was born in the 17th century. She married Emperor Muro III circa 1666, but on her wedding night she was reportedly killed by poison. In reality, medical testing showed her to have powerfully regenerative cells that would give her an extended lifespan and near invulnerability. Scared that she would be considered a freak of nature rather than a person, Muro staged her death and hid her away until a royal retreat on Mila Xa could be rebuilt as their private paradise.
In 1669, Muro was reported to have disappeared during a space expedition. He and Saeena then reunited on Mila Xa and spent the rest of their time together. The asteroid used holographic projections of witches, a ghostly version of Saeena and zombie robots to frighten away interlopers. Muro died at age 84, but Saeena lived on.
In 2266, senior scientist Doctor Krisp and a landing party from the USS Enterprise explored the asteroid, eventually traveling six miles below the surface to discover a hidden sanctum. They were the first people to see Saeena in 600 years. She said nobody was allowed to leave the asteroid, but they were welcome to spend their lives in happiness here, as had all the missing grave robbers. However, the asteroid was set to self-destruct the moment she died, and the landing party departed just in time to avoid the detonation. (TOS comic: "The Haunted Asteroid")
Kirk later recalled his experiences at Mila Xa in a letter to the commander of Starfleet Archives Records Section. Kirk thought it was amazing that Saeena had lived alone for hundreds of years. (The Enterprise Logs, Volume 3)