List of causes of regeneration

The causes of regeneration, especially amongst Time Lords, were many and varied. They ran the gamut from simple desire to change, to life-threatening maladies which typically resulted in human death. The following are the known causes of regeneration of specific Time Lords.

Romana

 * First to second incarnation: Decided it was time for a change, another account said unknown to the Doctor, Romana was harmed by the Key to Time. (TV: Destiny of the Daleks, AUDIO: Lies, The Key 2 Time - The Chaos Pool, PROSE: The Lying Old Witch in the Wardrobe)
 * Second to third incarnation: In one timeline she regenerated in preparation for the Second War in Heaven, developing a body and attitude more suited for combat. (PROSE: The Shadows of Avalon). In another timeline she regenerated to give a power boost to the Moros engine shields in order to stop a black hole being formed. This regeneration was rewritten due to the her Third Incarnation wanting to stop the Omega war. (AUDIO: Enemy Lines)
 * The second incarnation once started to regenerate due to contact with the decaying Eye of Harmony inside the Matrix. (AUDIO: Renaissance). This regeneration didn't take hold due to K9 Mark II removing her from the Matrix. (AUDIO: Ascension)
 * Third to fourth incarnation: Managed to survive the Second War in Heaven, although this may have entailed a regeneration. (PROSE: Tomb of Valdemar)

The Master

 * Note: Other occasions in which the Master has appropriated a new body, (TV: The Keeper of Traken, Doctor Who, COMIC: The Glorious Dead, AUDIO: Mastermind) are not considered regenerations.

Rassilon

 * Rassilon was said to have achieved immortality in the form of a "Timeless, perpetual, bodily regeneration." (TV: The Five Doctors) He appeared to have been reduced to a mind within the Matrix, (AUDIO: Zagreus) but he was able to manifest a new body in his workshop, and was later restored to full corporeal form to lead Gallifrey in the Time War. (PROSE: Engines of War)
 * Rassilon was attacked by with powerful energy blasts as the Time Lords were sent back into the Time War by the Tenth Doctor, (TV: The End of Time) and had regenerated into a much older body by the time of the Twelfth Doctor's finding of the planet. (TV: Hell Bent)

K'anpo Rimpoche

 * K'anpo Rimpoche was attacked by the Eight Legs on Earth. He regenerated into the form of Cho Je, a projection of his own mind. (TV: Planet of the Spiders)

Borusa

 * Borusa regenerated at least three times, and had at least four incarnations. (TV: The Deadly Assassin, TV: The Invasion of Time, TV: Arc of Infinity, TV: The Five Doctors) After being retro-evolved into the possibility engine, he was trapped in an iterative regenerative loop, his body transforming into each of his thirteen incarnations in turn. (PROSE: Engines of War)

Chronotis

 * Salyavin used up his thirteenth and final incarnation when he was attacked by the Sphere. However, when his Type 12 TARDIS was sent backwards, it altered his personal timeline and brought him back to life. (HOMEVID: Shada/WC: Shada)

Ailla

 * Ailla was accidentally shot by Koschei while he was fighting with Imperial forces in the Darkheart; although badly injured and apparently dead (Based on examinations of her assuming that she was only human), she was able to survive in her damaged body until she returned to Koschie's TARDIS and regenerated in the Zero Room (PROSE: The Dark Path)

Rallon

 * Rallon initiated all twelve of his regenerations at once to force the Celestial Toymaker out of his body; his Watcher subsequently merged with the Toymaker to keep him in check in future, the Doctor noting that this would mean that the Toymaker himself had essentially regenerated as a person. (PROSE: Divided Loyalties)

Roche

 * Lord Roche was caught in a traffic accident while on Earth; he retained enough control over the process after it began to deliberately shape his new appearance so that he was the exact duplicate of the Third Doctor. (PROSE: The Suns of Caresh)

Azmael

 * In his thirteenth and final body, Azmael deliberately regenerated past his limit, killing him and Mestor, who had been attempting to possess Azmael's body after his own was destroyed. (TV: The Twin Dilemma)

Iris Wildthyme

 * Iris Wildthyme regenerated after a lengthy period of illness following the consumption of a live Kaled mutant. (PROSE: The Scarlet Empress)

The War Chief

 * The War Chief underwent a faulty regeneration after being shot by War Lords; lack of medical care and the scale of the damage sustained resulted in his new form appearing like two bodies fused together, the damage preventing him from ever regenerating again. (PROSE: Timewyrm: Exodus)

Ruath

 * Ruath drained every drop of her blood from her body to restore Vampire Lord Yarven. Yarven subsequently turned her new incarnation into a vampire. (PROSE: Goth Opera)

Innocet

 * Innocet was killed by a Quences-possessed Badger to protect the Doctor. (PROSE: Lungbarrow)

Glospin

 * Glospin was stated to have regenerated at least twice before the events of his scheme against the Doctor.
 * Glospin force-regenerated himself into the double of the Doctor after acquiring a genetic sample to influence the appearance of his next incarnation (PROSE: Lungbarrow).
 * Having killed Quences in 'disguise' as the Doctor, Glospin regenerated again to conceal his role in the murder (PROSE: Lungbarrow).

I.M. Foreman

 * As a priest, I.M. Foreman had been given the gift of regenerations. This made twelve different individuals, who were created by his body absorbing the DNA around him; all regenerations were caused by the Third Doctor sending Foreman's first twelve bodies back to Gallifrey's past so that they fell from a great height, each regenerating into their next body, the trauma of the regeneration causing each incarnation to lose their memories. (PROSE: Interference - Book One, Interference - Book Two)

Cavisadoratrelundar

 * A Time Lord agent, Cavis nearly regenerated after she was decapitated by Queen Regent Mab, but Mab also stabbed her in both hearts to ensure that she remained dead. (PROSE: The Shadows of Avalon)

Gandarotethetledrax

 * A Time Lord agent, Gandar was stabbed in the heart by Margwyn, but regenerated as Margwyn missed his second heart. (PROSE: The Shadows of Avalon)
 * Gandar regenerated again shortly after his previous regeneration when he received a fatal sword wound; his new incarnation resembled a hybrid of human and Silurian, and was far more peaceful than his previous violent selves. (PROSE: The Shadows of Avalon)

Louis

 * Louis's first regeneration was triggered by a staser-gun blast inflicted by Rigan. (AUDIO: Unregenerate!)

Klyst

 * A comment by Professor Klyst that the first regeneration was always more painful than subsequent ones suggested that she was in at least her third incarnation. (AUDIO: Unregenerate!)

Elbon

 * Surgeon-Master Elbon was shot by a servitor that Irving Braxiatel placed in the TARDIS that Romana II used whilst trying to bring a pair of Pig-rats back to Gallifrey. His next incarnation was hijacked by the Dogma Virus. (AUDIO: Panacea)

The Corsair

 * The Corsair regenerated several times, with "a couple" of his incarnations being female. He was back to male by the time he was killed by House. They either created or acquired the same snake tattoo in each incarnation, appearing in a new place on their new body. (TV: The Doctor's Wife)

Karlax

 * Karlax was forced to regenerate having been exposed to the space vacuum after Dalek stealth ships destroyed his Battle TARDIS during the Last Great Time War. (PROSE: Engines of War)

Ollistra

 * When the Eleven came to New York to confront Ollistra and the Eighth Doctor, she was pushed from a building by him, which triggered a regeneration. (AUDIO: The Side of the Angels) This new incarnation would later confront the War Doctor multiple times during the Last Great Time War. (AUDIO: The Innocent et al.)

The General

 * The General had already regenerated ten times before his sole male incarnation led the War Council during the final day of the Last Great Time War. Later, the Twelfth Doctor, after asking him for his regeneration number so as to make sure that he would not kill him, triggered an eleventh regeneration in the General by shooting him with a sidearm belonging to the President's personal guard, resulting in the General returning "back to normal" as her twelfth incarnation emerged in a female form once more. (TV: Hell Bent)

Thessalia

 * Chatelaine Thessalia forced herself to regenerate after the Imperator's trial by putting a gun in her mouth and committing suicide. (PROSE: Newtons Sleep)
 * She regenerated again, growing younger and taller, sometime before recruiting Larissa to the Order of the Weal. Larissa speculated this occurred during the worldquake or the goblin infestation. (PROSE: Newtons Sleep)

Pavo

 * Constable Pavo was shot by The Monk; the Monk used a perception-altering ring to pose as Pavo while Pavo regenerated into a female incarnation with the aid of the Second Doctor and Jamie McCrimmon, the new Pavo posing as Commander Melanie Flail until the time came to reveal her true identity and survival to the Monk (AUDIO: The Black Hole).

Trave

 * Trave was shot in the line of duty when posted to Outpost Delta. She regenerated into a Male form. (AUDIO: Enemy Lines)