Tzim-Sha

Tzim-Sha, (PROSE: The Secret in Vault 13) also spelt T'zim-Sha, (WC: Case File One) was a Stenza warrior who sought to become the leader of his people. He was nicknamed "Tim Shaw" by the Thirteenth Doctor, due to her mishearing his true name. (TV: The Woman Who Fell to Earth) He was continually referred to as Tim Shaw, such as when Yaz spoke about him on Desolation (TV: The Ghost Monument) and when confronted by Team TARDIS on Ranskoor Av Kolos. (TV: The Battle of Ranskoor Av Kolos)

Hunting Karl Wright
He used a swarm of gathering coils in order to locate a trophy to take back to his planet, despite this being against his species' rules so he could win the leadership of his people.

He came ahead in his pod, waiting inside for the coils to find his target before breaking out and killing Rahul, taking one of his teeth as a prize. He then began searching for the coils in order to learn where and who his target was. While searching for the coils, he encountered Dean, who threw salad at him, mocking his appearance. Angered, Tzim-Sha killed him and took one of his teeth as well.

Upon finding the coils, he was confronted by the Doctor, along with Ryan, Graham, Grace and Yasmin who ordered he not hunt on Earth and flee back to his people. However, Tzim-Sha refused, threatening to kill the Doctor if she tried to stop him. He absorbed the data and then used a short-range teleport to reach his target, Karl Wright, at a construction site.

There, he killed the security guard and proceeded to climb up Karl's crane to reach him. However, the Doctor arrived with assistance and proceeded to convince Karl to leave his crane and climb towards her so he could jump to safety. However, Tzim-Sha caught up to them, grabbing Karl to take back with him. Not giving in, the Doctor leapt across, stating he couldn't leave as she had stolen the recall device from his pod that would allow him to return home and threatened to destroy it. Calling her bluff, Tzim-Sha detonated the DNA bombs his coil implanted in the Doctor and the others.

However the detonation affected him instead as the Doctor has transferred the bombs into the coil's data, meaning Tzim-Sha had downloaded them. With no choice, Tzim-Sha let Karl go and took the teleport to flee back to his planet, but not before Karl kicked him off the railings. (TV: The Woman Who Fell to Earth)

Exile on Ranskoor Av Kolos
As the recall device had been corrupted, the teleport took him instead "halfway across the universe" to Ranskoor Av Kolos where he wouldn't be able to leave without dying. However, Ux Andinio mistook him for their creator and thus helped him regain his health and strength though he required a life support machine. Tzim-Sha was able to use the hive knowledge of the Stenza held within him combined with the Ux's dimensional engineering capabilities to build up an army of SniperBots and other Stenza technology.

Over thousands of years, Tzim-Sha combined all the knowledge of the Stenza with the abilities of the Ux to create a weapon capable of trapping entire planets in stasis. With this weapon, Tzim-Sha trapped five different planets, committing genocide of all of the people on each one. This atrocity caused the Congress of the Nine Planets to send fleets of ships to Ranskoor Av Kolos to stop Tzim-Sha, but they fell to Tzim-Sha's forces. Eventually, Greston Paltraki arrived with his crew and managed to steal one of the planets held in stasis by Tzim-Sha, but his crew was captured in the process and made into Stenza trophies of which Tzim-Sha had around thirty.

Three thousand four hundred and seven years after Tzim-Sha first became trapped, Team TARDIS picked up nine distress calls from Ranskoor Av Kolos and landed on the planet to investigate, meeting Paltraki whose mind had become muddled by the effects of the planet. Shortly after the Doctor gave Paltraki a neural balancer to help fix his mind, Tzim-Sha contacted Paltraki and demanded the return of the stolen planet, executing one of Paltraki's crew in front of him and threatening to brutally murder the rest if he didn't comply. The Doctor and her companions were left in shock to recognize their old enemy, having believed Tzim-Sha to have been sent back to his homeworld when they last met.

The Doctor, her companions and Paltraki set out to stop Tzim-Sha and his plans. The Doctor was brought in front of Tzim-Sha by Andinio where Tzim-Sha explained what had happened since they had last met and his motives. Tzim-Sha then had the Ux turn the weapon on Earth, intending to destroy the planet and the human race in retaliation for his previous defeat, ignoring the Doctor's warnings that the technology was not stable and using it on another planet could destroy everything. Tzim-Sha declared that he would target any planet that ever defied the Stenza and use his weapon on them.

As the Ux used the weapon on Earth, Tzim-Sha received a warning that Graham O'Brien and Ryan Sinclair were freeing his trophies and went to stop them personally. By the time he arrived, Graham had destroyed his army of SniperBots and the prisoners were free and on their way to Paltraki's ship. Though Graham had sworn to kill Tzim-Sha if he ever saw him again, he couldn't bring himself to pull the trigger. Instead, when Tzim-Sha threatened Ryan, Graham shot him in the foot, incapacitating Tzim-Sha who was then taken captive by the two men. Having managed to stop the destruction of Earth, the Doctor was able to combine the powers of the Ux, Tzim-Sha's Stenza technology and her TARDIS to return the planets Tzim-Sha had stolen back to their proper places in space.

With Tzim-Sha's plan thwarted, Graham and Ryan decided that he wasn't worth killing, stating that Tzim-Sha instead deserved a taste of his own medicine. Graham and Ryan sentenced Tzim-Sha to life imprisonment in a Stenza stasis chamber, once used for Tzim-Sha's trophies. The two ordered him to keep the name of Grace O'Brien in his mind as he contemplated eternity. The Ux subsequently sealed the building so that no one could ever reach Tzim-Sha and free him from his eternal prison. (TV: The Battle of Ranskoor Av Kolos)

Behind the scenes
This character's name was given several different ways by official sources. He was listed by his Doctor-given nickname "Tim Shaw" in the credits for TV: The Woman Who Fell to Earth and in some BBC marketing elements. In at least BBC America, ABC iView and iPlayer closed captioning, the non-English variant is rendered as Tzim-Sha.

A Case File video about the Stenza also calls the character "Tim Shaw" but renders the real name with an apostrophe: T'zim-Sha. Because the font used in this Case File is all uppercase, however, even it doesn't settle whether the real name should be T'zim-Sha or T'Zim-Sha.

Finally, the children's novel The Secret in Vault 13 confirmed Tzim-Sha as the spelling, which would later be used on television via the credits for TV: The Battle of Ranskoor Av Kolos.