Tzim-Sha was born with five other pups, and as a boy the then leader
Raida launched a campaign against the clans of leaders who disagreed with him. He belonged to one of these clans, and was old enough to remember each and every member marched onto the Ice Flats by their fellow Stenza soldiers. He escaped by standing stock still, slipping under the Flats and watching the bodies fall through. When all fell silent, he pulled himself out of the Flats and began to wander around the settlements in the hills around the Ice Flats.
In
Strares, he found
Creyth, who was and is the Elder of the
Clan of the Lost. Creyth took him in, along with almost a hundred other pups and children who escaped the clan killings over that winter, and gave Tzim-Sha his current name. Creyth worked with one other man to assassinate Raida, and when that succeeded another had to be chosen.
As he grew, Creyth noted that he was unable to attach himself to his new clan, as he remembered who he was born to, and the way they died. So, Tzim-Sha devoted himself to the pursuit of rank. He saw that people in power could get away with virtually anything, and perceived it as a form of personal protection, so he committed himself to attaining standing by any means necessary.
This culminated in the night he cheated to challenge for leader, using a sophisticated gathering coil designed to locate his target for him so that he could spend as little time as possible seeking out the chosen human. This fell apart when he met the Doctor, after she regenerated and fell from the sky. While recovering from the regeneration, the Doctor and her new companions pieced together his plot, rescued his target, and attempted to send him back to
Mudewei.
There were a couple of problems: The Doctor and her companions were implanted with DNA bombs, which the Doctor had to figure out how to remove. Secondly, Tzim-Sha's recall device was corrupted, depositing him on the planet known as Ranskoor Av Kolos. He was found there by the two living Ux,
Andinio and
Delph. Andinio, who had been training Delph, mistook Tzim-Sha for the Ux's god, the Creator. Tzim-Sha exploited this, though his first task was to recover from the detonated DNA bombs and be pieced back together.
After this arduous process, he devoted his time to the development and testing of a large shrine/weapon, something capable of placing a whole planet into stasis (as opposed to a human, or other species, trophy). Over time, living on a planet that sends out psychotropic waves that alter memory and personality, and living with the Ux, at least one of whom worshipped him, he developed the idea that their powers were his (at least to command). By the time he met the Doctor again, 3407 years later, he had shrunken down and captured five planets. The response to this until the TARDIS landed (responding to nine individual distress calls from that region), had been for the Congress of the Nine Planets to send fleets of ships in an effort to stop him. None were successful until Captain Paltraki and the Doctor.
The Doctor and her companions freed Tzim-Sha's hostages, including Andinio and Delph (over Andinio's protests), and used the Ux's powers to return the stolen planets to their places. Meanwhile, Graham shot him in the foot (having originally intended to kill him for the death of Grace during their first meeting), and he and Ryan imprisoned him in one of his own stasis chambers.
Some time later, a tear through space and time formed in his stasis chamber, and a slight movement of the planet, going about its natural course, pulled him through it. He was deposited in
Esterholt, Ohio, in the year 2499, to be found by
Ta'zhen.
Yeaah, I don't know how to feel about him. But he's so close to Ta'zhen. But I don't think I like him.
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If it makes you feel any better, she doesn't like him half the time. They may be culturally bound but that doesn't mean they have to like each other. (Kind of like IRL siblings, from what I can gather.)