The sonambutron was under a landmass later known as Mount Idyll; its life support system was powered by the planet's geothermal energy and equipped by a defensive mechanism: androids would fend off intruders, created by a machine which telepathically drew from minds the most feared enemy.
The machine was programmed to re-activate again by the gravitational pull of the next solar eclipse, however they would not predict that in the meantime the planet's moon would be destroyed.
For the remaining millennia they remained in slumber until an away team of the USS Enterprise with Captain James T. Kirk, Spock, Dr. Leonard McCoy and Ensign Everts arrived on the planet to investigate. They discovered the doorway into the sleeping complex and, having shot the guardians who had taken the form of Klingons, managed to reactivate the machinery. (TOS video game: Star Trek: 25th Anniversary)