Sooal was a Caarian.
In 1979, he hijacked the spaceship the memory-erased Tulkan War Council was on and brought it to Earth. He bought Graystairs, converting it from a convalescent home to an Alzheimer's disease treatment facility. This was a cover for his experiments to restore the Council's memories and obtain the access codes to the stasis chamber where the Council had stored weapons.
However, Sooal had progeria and really wanted the metabolic stabilizer in the chamber to enable him to live a normal lifespan. He encountered the Seventh Doctor in 1982. The Doctor adjusted the settings of the transmat Sooal was using so that when he went through, he appeared in the chamber and was frozen in time. The power to the chamber would last ten thousand years, according to the Doctor. What happened at that point is unknown. (PROSE: Relative Dementias)