The Trickster

The Trickster was an immortal extra-dimensional alien, formerly part of an extra-dimensional group of beings known as the Pantheon of Discord, who were banished from the known universe. The Trickster, alone, frequently appeared on Earth, making bargains to alter history and feeding on the resultant chaos. An alternation made over a weak point in space-time would allow the Trickster to manifest himself as flesh and blood.

Biography
Not much was known about the Trickster's origin, other than he was affiliated with the group known as the Pantheon of Discord. All that was recorded were his attempts to influence history. Legends of the Trickster and the Pantheon were known to the Time Lords. (TV: The Wedding of Sarah Jane Smith)

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 if he gave him his consent. Krislok agreed, and the Trickster rescued him. In exchange for saving him, the Trickster forced Krislok to become his slave. (TV: The Temptation of Sarah Jane Smith)

First attack
Later on, to satisfy his hunger for chaos, the Trickster found an event in 2008, which would have caused destruction on Earth and wiped out humanity, who would otherwise become a major species in the universe. This event was a meteorite crashing into the Earth, which had gone undetected by military radar. (TV: Whatever Happened to Sarah Jane?) There were many other times when life on Earth would have been threatened by extra-terrestrial factors (TV: Invasion of the Bane, Revenge of the Slitheen, Eye of the Gorgon, et al), but the impact of the meteorite was one of the few with no determinable purpose, being the result of pure chance. Upon consuming the resultant chaos, the Trickster would thereby possess enough energy to manifest himself in N-space. (TV: Whatever Happened to Sarah Jane?)

In the original timeline, the impact would have been stopped by Sarah Jane Smith and Mr Smith. In order to prevent this and ensure humanity's destruction, the Trickster removed Sarah Jane from the timeline by manipulating her childhood friend Andrea Yates, who had died after falling from a derelict pier in 1964. Accompanied by his Graske servant, Krislok, the Trickster approached Andrea at the moment of her death and offered her the chance to allow Sarah Jane to die in her place. In this now-altered timeline, Andrea accepted the Trickster's offer - the girls' places were exchanged and Sarah Jane perished.

In order to prevent humanity's destruction occurring by any means other than the meteorite, the Trickster also "turned away" all of the aliens that Sarah Jane encountered in the original timeline. As a result, Luke Smith (Sarah Jane's adopted son), was never born because the Bane never invaded Earth. Through Sarah Jane's memories, the Trickster also learned of the existence of the Doctor, and taunted Sarah Jane about using her to remove him from time as well, which would have resulted in untold chaos for him to feed on.

However, all did not go to plan. Before the Trickster removed her from history, Sarah Jane had entrusted Maria Jackson with an alien puzzle box which protected her from the effects of the Trickster's interference, allowing her to remember the original timeline. She reminded Andrea Yates of the day that Sarah Jane had died in the altered timeline, causing Andrea trauma. Claiming to only desire Andrea's happiness, the Trickster offered to remove Maria from history. Upon her agreement, he sent Krislok to transport the girl to limbo. However, Maria's father, Alan Jackson, found the dropped puzzle box prior to Maria's removal from the timeline, allowing him to remember his daughter. Alan, in turn, reminded Andrea of Maria, again causing her distress. The Trickster sent Krislok after Alan, but he was able to ambush the Graske using his stakeboard and tie him up.

Alan found a device on Krislok which summoned Maria back to existence from Limbo, and they went to 13 Bannerman Road where Sarah Jane appeared in the mirror in Andrea's attic. She explained that while Andrea was alive, Sarah Jane couldn't be. Andrea, realising that her death was now inevitable (either by falling off a pier in 1964, or from the imminent meteorite impact), repudiated her deal with the Trickster. The timeline returned to normal - Sarah Jane Smith was restored and Mr Smith deflected the incoming meteorite away from the Earth. Thus, the Trickster's plan was foiled. (TV: Whatever Happened to Sarah Jane?)

Revenge on Sarah Jane
The Trickster decided to get revenge on Sarah Jane Smith. With the help of his servant, Krislok, he opened a time portal to the village of Foxgrove in 1951. This gave Sarah Jane the opportunity to meet her parents, whom she did not remember due to their deaths in a car crash when she was an infant. Sarah Jane disabled her father's parked car with her sonic lipstick, stopping her parents from driving to their deaths. However, by preventing a fixed event in history, Sarah Jane had inadvertently weakened Foxgrove in space-time, which allowed the Trickster to use the site as an anchor to manifest himself in physical form. This created an alternate future in which the Trickster turned the Earth into a barren wasteland; his Graske, Krislok, had enslaved what remained of mankind, forcing them to mine for minerals which would give the Trickster enough power to escape into space and enslave other planets. However, Rani Chandra and Clyde Langer were able to strike a bargain with Krislok, giving him Sarah Jane's puzzle box in exchange for Krislok reopening the time portal. Now protected from the Trickster by the puzzle box, Krislok departed, finally free of his master. Rani then travelled through the portal to 1951, and warned Sarah Jane of the Trickster's plan. Having realised that their deaths would save the world from the Trickster, Sarah Jane's parents sacrificed themselves, which restored the original timeline. Once again, the Trickster was defeated. (TV: The Temptation of Sarah Jane Smith)

An uninvited wedding guest
When Peter Dalton fell down the stairs at home and was about to die, the Trickster — clad in white as opposed to his usual black — appeared to him and asked for his agreement. If he agreed, he would survive but would have to get Sarah Jane to marry him, which he did. However, the wedding was disrupted by the sudden arrival of the Tenth Doctor, who had learned of the Trickster's plan and demanded the wedding be stopped. At this point, the Trickster trapped them in two time loops, with Peter and Sarah Jane in one and the Doctor, Luke, Clyde, Rani and K9 in another. If Sarah Jane did not agree to the wedding, then they would all be trapped forever. If married, Sarah Jane would stop fighting aliens, and chaos would ensue.

The Doctor's TARDIS tried to get into the time loop, and the Doctor was able to get inside, but the TARDIS was pulled out of the loop before the others could be saved. When Clyde inadvertently absorbed residual Artron energy from the leaving TARDIS, he made physical contact with the Trickster, weakening them both with the energy. He and Clyde were sent back in the reception room as the Doctor arrived. When Peter learned the full story and the consequences of his action, he repudiated his deal and threw his ring at the Trickster, banishing him. (TV: The Wedding of Sarah Jane Smith)

Sarah Jane's memorial
During a remembrance of Sarah Jane after her death, the Trickster's servants, the Jackals of the Backwards Clock, infiltrated the service by pretending to be waiters. They had a plan to swap the planet Earth with a vile copy from the septic dimension, but were thwarted in ten minutes by the attendees of the service – many former companions of the Doctor and of Sarah Jane Smith – who managed to shrink the Trickster down to the size of a doll, lock him in a treasure chest and send him to the bottom of the Atlantic Ocean for the next thousand years. (WC: Farewell, Sarah Jane)

Other influences
There were other members of the Trickster's Brigade. One was a beetle-like creature which created a parallel world around Donna Noble in which the Tenth Doctor died. This resulted in much chaos due to alien attacks and incursions on Earth not being thwarted. (TV: Turn Left) Others organised a plot involving a Brainspawn driving future American President Franklin Delano Roosevelt insane, causing him to drop America out of World War II resulting in Nazi Germany winning the war. This plan was foiled by Jack Harkness and Angelo Colasanto. (TV: Immortal Sins)

When cyborg hacker Psi was attempting to protect Clara Oswald from the Teller, he ensured that it would focus on his guilt by uploading the memories of some of the worst criminals in history, one of them being the Trickster. (TV: Time Heist)

Personality
The Trickster was an enigmatic and sinister creature that was perpetually hungry for chaos, which served as his "blood, air and food". He revelled in the chaos, or the representations of chaos, that his plots created - he derided all other species for threatening Earth out of profit, power or revenge, but praised the pure chaos of a meteor that would destroy Earth by blind chance. He also cruelly contemplated the extent of the chaos that he could create by removing the Doctor from the universe.

The Trickster was highly intelligent and manipulative, capable of influencing most sentient beings with words alone. He achieved this with seductive offers of letting his victims live happily, but at terrible hidden cost. He was apathetic and arrogant, considering himself superior to other beings and caring only for his consumption of chaos. This proved to be his downfall each time he faced Sarah Jane Smith; he was incapable of understanding, or even considering, the full extent of sentient beings' emotions. The Trickster depended on his victims' natural instinct to survive, especially at the expense of others, when trying to manipulate them. As such, he often forgot (or was incapable of recognising) a victim's capacity for selflessness.

The Trickster developed a deep hatred for Sarah Jane Smith. This started when his initial plan to manifest himself in N-space was foiled by Sarah Jane and her friends. Although the Trickster was successful in removing Sarah Jane from history (by manipulating her friend Andrea Yates), he was prevented from feeding on the chaos that Earth's destruction would have reaped because Andrea reneged on her agreement with him. Enraged but powerless to stop the restoration of the original timeline, the Trickster silently returned to limbo.

The Trickster's next altercation with Sarah Jane Smith was directly vengeful and thus much crueller. He preyed upon Sarah Jane's emotions surrounding her parents to the point where he successfully tricked her into altering history to save them. This weakened the Web of Time sufficiently for him to physically manifest himself, which allowed him to decimate the Earth and then feed on the chaos he had created. He showed open glee at Sarah Jane's apparent defeat on this occasion, taunting that she had given the planet over to him and allowed him to destroy it almost willingly. He also openly gloated over his victory, attempting to convince Sarah Jane that their battle was already over. However, the Trickster later showed his inconsideration (or ignorance) of selflessness once again, as he had not expected Sarah Jane's parents to be willing to prevent his manifestation and reset the timeline by sacrificing themselves.

Upon his third attempt to manifest himself and neutralise Sarah Jane Smith, the Trickster was far subtler in his manipulation than before, using Sarah Jane's capacity for love against her. The Trickster had forseen that if Sarah Jane were to marry her perfect romantic match, she would be distracted from her life defending the Earth and many threats to the planet would thus go unchecked, resulting in chaos. By donning white robes instead of his usual black, the Trickster approached and seduced Peter Dalton into saving himself from death. The Trickster then convinced Peter to seek out and marry Sarah Jane Smith, as a condition of their agreement. However, for the third time in a row, the Trickster's victim turned against him, as Peter withdrew his prior agreement. The Trickster even commented on Peter's surprising resilience as his form was returned to the limbo dimensions.

The Trickster was a sadistic being, taunting the Tenth Doctor's loneliness, and ignorance of "the Gate" that awaited him. He also arrogantly and contemptuously observed that the Doctor, whom the Trickster had thought to be powerful, appeared to need the support of three human children. However, this insult did also highlight the Trickster apparently ignoring or being unaware of the fact that all three children had been involved in his prior defeat.

Abilities
The Trickster was an incredibly powerful creature. He fed on chaos and acted to increase random chaos purely because it empowered him. He had less interest in the chaos created by intelligent beings, preferring the chaos of natural disasters. (TV: Whatever Happened to Sarah Jane?) The Trickster was also extremely manipulative; he had power to alter the personal timelines of sentient beings, but only with their express consent. He tended to go after the dying, giving them life in return for servitude. People and things removed from the timeline by his alterations would find themselves trapped in limbo. (TV: Whatever Happened to Sarah Jane?, The Temptation of Sarah Jane Smith, The Wedding of Sarah Jane Smith) He was vulnerable to Artron energy, which the Doctor described as "equal and opposite of the Trickster's power". (TV: The Wedding of Sarah Jane Smith)

The Trickster also seemingly had the power to forsee future events in a being's personal timeline; he knew of the Tenth Doctor's interaction with the Immortality Gate before the Doctor himself encountered it. (TV: The Wedding of Sarah Jane Smith)

Appearance
The Trickster had a humanoid form, but with sharp teeth and an otherwise featureless face. The Trickster normally wore a long black hooded robe and gloves, covering his entire body apart from his face. (TV: Whatever Happened to Sarah Jane?, The Temptation of Sarah Jane Smith) Whether this was his true form or an attempt to cause fear is unknown. (TV: SJAF 1) When he appeared to Peter Dalton under the pretence that he was a benevolent angel there to help, he wore the same outfit, but the colour was entirely changed to white; resuming his more customary black only while apart from Peter and Sarah Jane. (TV: The Wedding of Sarah Jane Smith)

He wore an ornate, silver full-finger ring. The Trickster appeared to channel his powers through this ring, using it to remove firstly Sarah Jane's car, then Sarah Jane herself from the timeline. (TV: Whatever Happened to Sarah Jane?)

Behind the scenes

 * The Trickster is the villain of a Doctor Who: Legacy storyline, named "The Trickster Event".
 * Initially the character's name was only given to the being by Alan Jackson as a description of him and was referred to by that title in the end credits. In The Temptation of Sarah Jane Smith, he called himself "the Trickster". He was specifically named "the Trickster" by the Tenth Doctor in TV: Turn Left and The Wedding of Sarah Jane Smith. Jack Harkness also referred to him as the Trickster in Immortal Sins.
 * A running gag occurs when the person realised the Trickster tricked them, they'll say "You tricked me!"
 * The Trickster would have returned in the series 5 finale The Battle of Bannerman Road. It would have been revealed he used a dimensional schism above the fleshkind world to gain fleeting access. He had instilled his essence in Sky Smith at the moment of her creation, and manipulated events so she would end up with Sarah Jane. He would then awaken Sky's "Trickster" half, and use her to attack Sarah Jane. He would then manifest using Sky and turn Sarah Jane's house into a giant tower that would spread over the world, and he would rule the world. Sky would later destroy him and guard his prison. (The Sarah Jane Companion Volume Three)
 * In The Wedding of Sarah Jane Smith, there were some shots in which small holes in the "eyes" areas of his face could be made out. These were presumably for Paul Marc Davies to see out of.
 * Russell T Davies has stated that the Trickster was witness to Harriet Jones' escape from the Daleks in Harriet Jones, PM, and that he "smiled as another piece in his long game fell into place... But that's a story for another time".