Roughly 4 billion years ago, the Jagaroth ship piloted by Scaroth landed on Earth. Advising not to take off at warp power three, the ship launched and became distraught from the power overload. Being in the warp control cabin, Scaroth was splintered in time when the ship exploded.
Twelve selves of him were scattered across time, though they could communicate through telepathy. The explosion, however, allowed the radioactivity that the primordial ooze needed for the Human race to exist. All throughout time, his selves pushed the Human race forward, showing Humanity fire, inventing the wheel, mapping the stars, and causing the pyramids to be built, all so that his twelfth self could have the technology to go back in time and prevent his splintering in time as well as the death of his race.
All of his selves, except for the Egyptian self, who appeared as a god on one occasion, disguised themselves as humans using a mask and skin into which he was able to fit himself.
In Florence, Italy in 1505, Scaroth appeared disguised as a human named Captain Tancredi. In this self, he convinced Leonardo da Vinci, a human painter, to paint six more copies of his famous painting, the Mona Lisa. He then stored them away for this later self to find.
His twelfth self was known as Count Carlos Scarlioni, a well known figure in the art world in 1979. Since he was involved, genuine art works that had been missing for centuries, like several Gutenberg Bibles, had started showing up. The Count was married to Countess Scarlioni, who never knew who he really was, thanks to little gifts every now and then and a little "excitement". He also designed a bracelet for her and asked her to wear it always.
Thanks to his other selves, he was able to use the artwork to fund his experiments with time, headed by Professor Fyodor Nikolai Kerensky. Having found the other six Mona Lisas, he planned to steal the one in the Louvre. He would then sell them to the seven people in the world who would pay anything for the Mona Lisa, and since the one from the Louvre would be stolen, they would all think they had the original, and Scaroth would make 100,000,000 dollars off of each of them.
He then met the Doctor and Romana when they tried to find the crack in time that his experiments caused. Romana was captured and made to build the field interphase stabilizer that would make the artificial time field Scaroth created stable, allowing him to travel back in time.
Having been convinced by the Doctor and by pictures of Scaroth's true self, the Countess turned against Scaroth. He then used her bracelet to kill her. Scaroth traveled back in time, his time only being two minutes, to try and stop the explosion that splintered him across time.
The Doctor reached there first with Romana and Detective Duggan, and was stopped when Duggan knocked him unconscious. His time came up and he faded back to 1979. When his servant Hermann saw his true form, he attacked Scaroth and he was destroyed along with his time field.