Not much was known about the Trickster's origin, other than the fact that he had parted ways with the group known as the Pantheon of Discord. All that was truly recorded was his attempts to influence history.
At some point, the Trickster learned that the Graske Krislok was destined to die, and set about trying to prevent this. Projecting an image of himself into Krislok's spacecraft, mere moments before it was about to burn up, the Trickster offered to save Krislok from death though only if he gave him his consent. Krislok agreed, and the Trickster rescued him. However, in exchange for saving him, the Trickster forced Krislok to become his slave.
Later on, to satisfy his need for chaos, the Trickster found one main event in 2008, which if it happened would have caused destruction on Earth and wiped out Humanity, who would later become a major species in the Universe. This event was that of a meteorite crashing into the Earth, undetected by military radars. There were many other times when life on Earth would have been threatened by alien life, however the meteorite crash was one of those few which had no purpose, it just being the result of pure chance. This would ultimately give the Trickster the opportunity to consume the resulting chaos, and manifest himself in reality in full power.
In the original time line, the impact would have been stopped by Sarah Jane Smith and Mr. Smith. To stop this, the Trickster removed Sarah Jane Smith from Earth's time line, influencing events so she died in the place of Andrea Yates (who should have died in the original time line) in 1964.
The Trickster also forced the aliens that Sarah Jane would have faced to leave the Earth alone. As a result, Luke Smith, Sarah Jane's adopted son, was never born because the Bane never invaded Earth. However, all did not go to plan. When removing Sarah Jane from history, one night Maria Jackson held an alien puzzle box, protecting her from the effects and allowing her to remember the original time line. She reminded Andrea Yates of the day Sarah Jane died, causing Andrea trauma. The Trickster sent his Graske servant Krislok to remove Maria and later removed her from history, however her father found and held the cube at the point of Andrea's consent, allowing him to remember the events. In turn, he reminded Andrea of Maria, again causing her distress. The Trickster sent Krislok after Alan, however Alan foiled the plan and trapped the Graske.
He discovered a device on Krislok which summoned Maria back to existence from Limbo, and the two headed to Sarah Jane's house (in this time line's, Andrea's) where Sarah Jane materialized in a mirror. She explained that while Andrea was alive, she couldn't be. Andrea, realizing that she had to die (either by falling off a pier in 1964 or in the soon-to-be meteorite crash), went back on her deal with the Trickster. The time line was back to normal, Sarah Jane and Mr. Smith deflected the incoming meteorite and the Trickster was defeated. Had his plan succeed, the Trickster revealed he also wished to use Sarah Jane to locate the Doctor and remove him from time, which would have resulted in an untold amount of chaos. He decided to get revenge on Sarah Jane as he opened a time portal to 1951 where she decided to meet her parents as she never had met them they had died when she was only three months old. Sarah Jane and Luke deactivated her father Eddie's car thus saving her parents from death. By creating this weakness in time by preventing a fixed event in history, the Trickster was able to physically manifest on Earth in nearby sacred ground, creating an alternate time line where the Earth was drained of its life by the Trickster, whose Graske, Krislok, enslaves mankind who mine for minerals to give the Trickster power to escape into space and enslave other planets. However, Rani Chandra travels back and warns Sarah Jane of the Trickster's plan to manifest, and her parents willingly sacrifice themselves to correct the time line. The nearly-corporeal Trickster seemingly explodes and dies. Although not actually present, the Trickster's Brigade encountered Donna Noble on the planet Shan Shen, and altered her timeline, creating a parallel universe around her, although this plan was ultimately foiled.Later, the Trickster returned, and crashed the wedding of Sarah Jane and Peter Dalton, but as the Trickster return as did Sarah Jane's old friend the Doctor, demanding that the wedding to be stopped. The Doctor revealed to Luke Smith, Clyde Langer and Rani Chandra that the Trickster was a member of the Pantheon of Discord, beings from beyond the Universe, who impressed themselves onto reality and thrived on chaos. He and the rest of his Pantheon appeared to have parted ways, for which the Doctor ridiculed him. When Peter Dalton fell on a staircase and was about to die, the Trickster came to him and asked for his agreement. If he agreed, he would survive but would have to get Sarah Jane to say "I do".
Sarah Jane would stop fighting aliens, thus would cause chaos. When the Trickster encountered the Doctor presumably the first time, he told him that "the Gate" was waiting for him, as well as saying that he was waiting for Sarah Jane's agreement. When Clyde absorbed artron energy from the TARDIS, Clyde attacked the Trickster, weakening them both. Both he and Clyde were sent back in the reception room as the Doctor arrived. Peter Dalton then went back on his deal and threw his ring into the Trickster and he was defeated. The Trickster could remove beings from, and influence the course of history. It had a mouth of sharp teeth, no eyes and was always hooded. Though in later appearances the eye areas appear have small growth or rips in them. It could materialise and dematerialise at will, appear only to certain individuals and appear either in reality or only in a mirror.
He could only influence reality with the consent of another, and otherwise was powerless, although should he ever manifest physically he would be nearly unstoppable.
For the most of his time Trickster remain calm and collected, taking a casual approch to both his nemesis and even the Tenth Doctor. While highly patient he is not above fits of anger when his schemes go wrong.
As an physical form of temtation and chaos he rarely interfers personally, rather manipulating or forcing other to do it for him.
The only flesh he reveals is his face, which is eyeless and very pale as well as having razor sharp teeth. The Trickster normally wore a long black hooded robe and gloves, covering his entire body apart from his face. When he appeared at Sarah Jane's wedding he wore the same outfit, but the colour was entirely changed to white, resuming his more customary black only while apart from Sarah. He wore white so as Peter Dalton believed he was an angel, in order to make him believe he was there to help and protect him and Sarah Jane.
Some time in the future there exists members of the Trickster's Brigade. One known member is a Fortune Teller on Shan Shen who used a beetle-like creature causing Donna Noble to experience an alternate time line in which the Doctor died.
By the 26th century some individuals worshipped the Trickster as the "God of Randomness".