After this he was tricked by Thorne to give him his regeneration unit for a lost memory chip. This turned him into a bomb to make him self-destruct on encountering Jixey. Starkey helped him disarm himself. (TV: Hound of the Korven) K9 Mark 2's brief life was almost cut tragically short when after the fall of the Korven invasion force, Thorne sent the Trojan to kill K9, who defeated it by burning out his power core and exhausting all his energy. As his regeneration unit was in the Trojan, K9 seemingly died at the mansion after his companions bade him farewell. However his regeneration unit homed in at the last minute and resurrected him, giving the frisky pup a new lease on life. The regeneration unit restored his old dog collar so he could celebrate the joyful occasion to the full as he flew off to more adventures, bristling with life. (TV: The Eclipse of the Korven)


When Romana eventually returned to her own universe, she brought K9 Mark II with her (presumably having repaired it) and eventually became Lady President of Gallifrey. K9 Mark II is first seen on Gallifrey in the Virgin New Adventures novel Lungbarrow by Marc Platt, alongside K9 Mark I, which had remained with Leela. Both K9 Mark I and Mark II appear, voiced by Leeson, in the Big Finish Productions audio adventure Zagreus and the Gallifrey audio series. Leela's K9 (Mark I) was destroyed at the conclusion of the second Gallifrey series and only Mark II appears in the third series.
In 1996, Sarah used K9 to hack into records and find Sam Jones' home address and later to translate Lost Boy's speech. (PROSE: Interference - Book One) K9 was briefly possessed by a malevolent entity, but was freed when Sarah accidentally electrocuted him. (PROSE: The Sow in Rut) K9 began slowly breaking down and eventually ended up deactivated in a cardboard box in Sarah's attic. (PROSE: Moving On) Hilda Winters had K9 dismantled and analysed. (AUDIO: Mirror, Signal, Manoeuvre)
Although the first incarnation of K9 does not appear again in televised Doctor Who media, he is the star of the 2009 K9 television series, in which he undergoes a sort of "regeneration" process from which a new, more sophisticated and futuristic K9 emerges;[1] in the first series of K9, the character is transported to London c. 2050 by Professor Gryffen (Robert Moloney). Though on regeneration the character loses his memory of his adventures with the Doctor, he assists Gryffen and several teenage companions against a dystopian regime of "The Department". The upgraded K9 has new specifications, sporting a sophisticated head-up display, the ability to fly, and more powerful laser weapons.
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