Artron

 was a Time Lord, and one of Rassilon's great engineers.

Artron energy was named after him.

History
Artron's work brought him to the Kolstan, a planet in the Time Vortex. There he was experimenting on the native Kolstani, and gained powers which many would later consider godlike. Later, he met, who he thought had been sent by the Time Lords. This was long before the Eighth Doctor's time, and indeed the Master's, and yet he encountered the two of them there. After the Doctor's arrival, the experiments of Artron and the Master lead to the destruction of the planet, and the creation of the Ravenous.

Using his powers, Artron transported himself and the Doctor to Earth's distant past, where the Doctor had claimed to be from. Shortly after, the Doctor realised that he'd previously heard of Artron in Salzburg, with Liv Chenka having met him. He then realised that having told Artron this, he had created his own future. the Doctor then disappeared, much to Artron's bemusement.

In the early 21st century, Artron had arrived in Salzburg as he had been told would happen. (AUDIO: Day of the Master) There he granted a wish, using his powers, to Maria Werner, who wished that the Krampus was real. He granted that wish, causing havoc to the city. He then encountered Liv, who asked him to reverse the effect of the wish, which he explained he could not do. Meeting her one more time, Liv asked for her wish. This wish was to make Helen young again, after she'd spent decades trying to save the city. (AUDIO: Better Watch Out, Fairytale of Salzburg)

A few million years later, Artron was dwelling in a tower in London. There, he was sought out by, who had also kidnapped Helen to help find him. After using his powers to evade being found, Artron eventually decided to chat to Helen, having recognised her. This meant he let his guard down, allowing Missy into the tower to stun him with her staser. As Helen was about to be killed by Missy, she used her wish to be with the Doctor and Liv, which also lead to the Doctor's disappearance earlier in Artron's timeline.

Arton was then taken to a Time Lord way station, which the Master had taken for himself, where they offered him to the Eleven on the Crucible of Souls in exchange for being spared from the Ravenous's current feeding frenzy. The Eleven attempted to offer him to the Ravenous, but they retained a fragmentary memory of his past kindness to them. While the Masters used the Crucible to reset the universe to normal, the Doctor was able to help Artron realise that he could restore the Kolstani by sacrificing his own power. Reverted to their original state by Artron's sacrifice, the Kolstani assured the Doctor that they would bury Artron somewhere peaceful. (AUDIO: Day of the Master)

Legacy
His brain-print was later stored in a tomb on Parrak. (AUDIO: Planet of Dust)

A massive statue of Artron was also built after his disappearance, which was prominently displayed in the Panopticon into at least the First Doctor's time on Gallifrey. (AUDIO: Day of the Master)