The Trickster

The Trickster was a mysterious entity which thrived on chaos and deliberately altered the known course of time.

Characteristics
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 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, (SJA: Whatever Happened to Sarah Jane?) although should he ever manifest physically he would be nearly unstoppable. (SJA: The Temptation of Sarah Jane Smith),(SJA: The Wedding of Sarah Jane Smith)

History
Nothing is known of the Trickster's origins, though given his behaviour, mannerisms, need for chaos and even certain words he has said many fans have been suspicious that he is the Black Guardian though this has not been confirmed or denied yet. All that is recorded is his attempts to influence history.

To satisfy its need for chaos, it found one main event in 2008, which if it happened would have caused destruction on Earth and wipedout 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 radar. There were many other times when life on Earth would have been threatened, however the meteorite crash was one of those few which had no purpose, it just being the result of pure chance.

In the original timeline, 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 timeline, influencing events so she died in the place of Andrea Yates (who should have died in the original timeline) in 1964.

The Trickster also stopped the aliens that Sarah Jane would have faced to leave the Earth alone, so Luke Smith was never born because the Bane never invaded.

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 timeline. She reminded Andrea Yates of the day Sarah Jane died, causing Andrea trauma. The Trickster hired a Graske to remove Maria and later removed her from history, however her father (Alan Jackson) 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 the Graske after Alan, however Alan foiled the plan and trapped the Graske.

He discovered a device on the Graske which summoned Maria back (from Limbo), and the two left the Graske and went to Sarah Jane's house (in this timeline, Andrea's) where Sarah Jane materialised in a mirror. She explained that while Andrea was alive, she couldn't be. Andrea, realising 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 timeline was back to normal, Sarah Jane and Mr. Smith deflected the incoming meteorite and the Trickster was defeated.

Had his plan succeed, the Trickster said that he also wished to use Sarah Jane to locate the Doctor and remove him from time, creating a lot of chaos throughout the Universe. (SJA: Whatever Happened to Sarah Jane?)

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 timeline 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 timeline. The nearly-corporeal Trickster seemingly explodes and dies. (SJA: The Temptation of Sarah Jane Smith)

Later, the Trickster returned, and crashed the wedding of Sarah Jane and Peter Dalton, but as the Trickster return so did Sarah Jane's old friend the Doctor. demanding that the wedding to be stopped. (SJA: The Wedding of Sarah Jane Smith).

Other influences
Some time in the future there existed members of the Trickster's Brigade, one such being a Fortune Teller on Shan Shen used a beetle-like creature connected that caused Donna Noble to experience an alternate timeline in which the Doctor (not to mention Sarah Jane Smith) died. (DW: Turn Left)

Behind the Scenes
The Trickster is similar to the Black Guardian, though, as yet, no formal connection has been made in the Doctor Who Universe. The character's name was only given to the being by Alan Jackson as a description of him, and as such the being was referred to by that title in the end credits. Its actual name, if it has one, is unknown, although in The Temptation of Sarah Jane Smith, it uses the name to describe itself.


 * The Black Guardian who was a Transcendental Being also embodied chaos.