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 sentencing for convictions, to life-threatening maladies, to blunt-force trauma. While all of these might have been cause for alarm in humans, Time Lords sometimes expressed much less concern. As the Twelfth Doctor once told Clara: "We're on Gallifrey. Death is Time Lord for 'man-flu'." (TV: Hell Bent)

That said, he was much less casual about regeneration when it came to his own—an event he fully tried to resist. (TV: The Doctor Falls) Though the First, (TV: Twice Upon a Time) Second, (TV: The War Games) and Tenth Doctors agreed with him, (TV: The End of Time) most incarnations of the Doctor were more at peace with regeneration. In particular, the Third, (TV: Planet of the Spiders) Fourth, (TV: Logopolis) Fifth, (TV: The Caves of Androzani) Eighth, (TV: The Night of the Doctor) War (TV: The Day of the Doctor) and Eleventh Doctors (TV: The Time of the Doctor) accepted their ends with varying degrees of equanimity.

The following are the known causes of regeneration of specific Time Lords.

The Doctor

 * First Doctor: Life force syphoned from him by the planet Mondas, forcing a regeneration from exhaustion and a loss of strength. (TV: The Tenth Planet) Although, the First Doctor held it back for a while as he feared regeneration. He decided to regenerate after a meeting with the Twelfth Doctor. (TV: Twice Upon a Time)
 * Second Doctor: Forced to change his appearance by Time Lord court order as punishment for stealing the TARDIS and breaking the non-interference law. (TV: The War Games) Execution eventually performed by animated scarecrows. (COMIC: The Night Walkers)
 * Third Doctor: Radiation poisoning upon prolonged exposure to the Great One's highly unstable web of Metebelis crystals (TV: Planet of the Spiders); drifted through time for ten years dying of the radiation poisoning before he returned to Earth (PROSE: Love and War) and had his regeneration triggered by K'anpo Rimpoche to compensate for the Doctor's body being unable to trigger it himself. (TV: Planet of the Spiders)
 * In a version of history created during the War, the Third Doctor's regeneration was caused by a fatal shot to the chest from Magdelana Bishop. The bullet entered his ribcage at an angle which didn't damage any major organs; he instead died of blood loss. (PROSE: Interference - Book Two)
 * Fourth Doctor: Fell to the ground from a great height after battling at the Pharos Project; merged with the Watcher to trigger regeneration. (TV: Logopolis)
 * Fifth Doctor: Contracted spectrox toxaemia on Androzani Minor, triggering regeneration. (TV: The Caves of Androzani) Regeneration completed after resisting 's attempt to stop his regeneration using their shared mental link to the now-destroyed Kamelion. (AUDIO: Winter)
 * Sixth Doctor: Either injured during an attack on the TARDIS by the Rani, (PROSE: Time and the Rani) blunt head trauma while suffering from chronon energy starvation after his confrontation with the Lamprey, (PROSE: Spiral Scratch) or intentional exposure to focused beams of a radiation lethal to Time Lords consequent to the Rani's attack on the TARDIS. (AUDIO: The Brink of Death)
 * Seventh Doctor: Following a non-fatal shooting, the Doctor was taken to a San Francisco hospital, where subsequent exploratory surgery with a camera accidentally clogged a vein; the anaesthetic he had been given delayed regeneration for several hours. (TV: Doctor Who)
 * Eighth Doctor: Died after a ship he was in crash-landed on Karn but was resurrected for four minutes by the Sisterhood of Karn. (TV: The Night of the Doctor) Tricked by Ohila into thinking the lemonade and dry ice he was drinking was the Elixir of Life, the Doctor regenerated when his four minutes were up. (PROSE: The Day of the Doctor)
 * War Doctor: Regenerative process triggered automatically due to old age. (TV: The Day of the Doctor)
 * Ninth Doctor: Directly absorbed Time Vortex energy from the Bad Wolf to save the life of Rose Tyler, causing fatal cellular degeneration. (TV: The Parting of the Ways)
 * Tenth Doctor: Grazed by the blast from a Dalek gun stick, causing a regeneration. However, the Doctor directed the regeneration energy to his severed hand, so aborted a full regeneration, healing the damage he had sustained without needing to actually change. (TV: The Stolen Earth, Journey's End)
 * Tenth Doctor: Radiation poisoning intentionally incurred in order to save the life of Wilfred Mott. (TV: The End of Time) Although, he held it back for a long period of time in order to revisit every one of his past companions. (TV: Death of the Doctor)
 * Eleventh Doctor: Neared death from old age after exhausting all of his regenerations. Granted a new regeneration cycle by the Time Lords. (TV: The Time of the Doctor)
 * Twelfth Doctor: Electrocuted by a Mondasian Cyberman, but delayed the regenerative process. Later shot repeatedly by another Cyberman and caught in a massive explosion, triggering the regeneration further. The regeneration was purposely delayed because he desired to not change again, (TV: The Doctor Falls) only accepting the change after a meeting with the First Doctor. (TV: Twice Upon a Time)

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 War, 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 prevented due to 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 War, although this may have entailed a regeneration. (PROSE: Tomb of Valdemar)

The Master

 * : Hit by a blast of artron energy when his attempt to attack the Twelfth Doctor backfired (COMIC: Doorway to Hell) or shot with his own Tissue Compression Eliminator by Susan Campbell. (PROSE: Legacy of the Daleks)
 * : Shot by Ace after receiving a new set of regenerating nanites from the Tzun. (PROSE: First Frontier) However, these were apparently only effective in the short term, as he was later shown attempting to restore his ability to regenerate using the Sacred Loom of Rassilon's Mouse. (PROSE: Happy Endings)
 * The child incarnation during the Last Great Time War: Regenerated into an after being unable to survive the energies at the heart of a paradox. (COMIC: Fast Asleep)
 * : Fatally shot by Chantho, he regenerated inside the Doctor's TARDIS after locking him out. (TV: Utopia)
 * : Stabbed in the back with a small knife by his in such a precise way that he had time to reach his TARDIS before regenerating (TV: The Doctor Falls) or mortally wounded while fighting Rassilon. (PROSE: Pandoric's Box)
 * Note: Occasions in which the Master has appropriated a new body, (TV: The Keeper of Traken, Doctor Who, COMIC: The Glorious Dead, AUDIO: Mastermind, And You Will Obey Me) 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) by having his Matrix projection imprinted on the Time Lord Valerian. (AUDIO: Desperate Measures)
 * 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 "stuffed his face full of White-Point Stars," causing Rassilon to regenerate (PROSE: Lords and Masters) into a much older incarnation. (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)

Chronotis

 * Salyavin used up all his regenerations 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. (WC: Shada, TV: Shada)

Ailla

 * Ailla was accidentally shot by Koschei while he was fighting with Imperial forces in the Darkheart; although badly injured and apparently dead, she was able to survive in her damaged body until she returned to Koschei'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 the 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)

The Eleven

 * In his eighth incarnation, who called himself the Eight, whilst hiding in the Clocksmith's TARDIS, he was discovered by the Clocksmith, who killed him. He went into the Doctor's TARDIS and regenerated into the Nine. (AUDIO: The Eighth Piece / The Doomsday Chronometer)

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 force-regenerated himself into the double of the First Doctor after acquiring a genetic sample to influence the appearance of his next incarnation. (PROSE: Lungbarrow)
 * Having killed Quences while disguised 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!)

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)

River Song

 * As a little girl, Melody Pond, later known as River Song, regenerated on the streets of New York City in 1970 due to a terminal illness. She ended up as a toddler upon her regeneration. (TV: Day of the Moon, Let's Kill Hitler)
 * In her second incarnation, known to Amy Pond and Rory Williams as Mels, Melody regenerated in Hitler's private study in 1938 after the Führer accidentally shot her while aiming for the Teselecta. She later used up all of her remaining regenerations to heal the Eleventh Doctor from a poison with which she had infected him. (TV: Let's Kill Hitler)

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)

Volstrom

 * In quick succession, Volstrom was forced to regenerate at least four times having been repeatedly shot by the Eleven using a staser modified to allow for regeneration as a means of torture, changing from male to female form then back to male then female again. (AUDIO: Songs of Love, The Side of the Angels)

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)

The General

 * The General experienced nine regenerations by the end of the Last Great Time War (TV: The Day of the Doctor) that all resulted in female incarnations. (TV: Hell Bent)
 * At some point before the end of the Last Great Time War, (TV: The Day of the Doctor), the General experienced a tenth regeneration that, uniquely to her previous regeneration experiences, resulted in a male incarnation. (TV: Hell Bent)
 * After tricking the Time Lords into saving Clara Oswald with an extraction chamber, the Twelfth Doctor tried to flee with Clara and armed himself with the General's sidearm. As the gun had no stun setting, the Doctor confirmed that the General had not yet completed his regeneration cycle before shooting him. The shot resulted in the General's immediate regeneration. To the General's relief, the new incarnation was once more a woman. (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: The Book of the War, 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)

Larissa

 * Larissa regenerated after being shot in the abdomen by Doctor Bendo. (PROSE: Newtons Sleep)

Pavo

 * Constable Pavo was shot by, who 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. (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)

Kallix
Causas de regeneraciones
 * Kallix regenerated after the Daleks attacked the Neverwhen. (AUDIO: The Neverwhen)