After stopping the Rani from releasing Omega and saving Poppy from being erased from existence, the Fifteenth Doctor underwent his regeneration into, presumably, the Sixteenth Doctor.
History[]
The cause[]
After the Fifteenth Doctor stopped the Rani and Conrad Clark from releasing Omega from the Under-Universe, the reality shifted reality back to normal. Conrad became a chef in the new timeline, and the Doctor gave Desidirium, the infant God of Wishes, to Ruby Sunday's foster mother, Carla Sunday. The ramifications of undoing the wishes would soon be noticed by only Ruby, as the knock-on effect also caused the Doctor's and Belinda Chandra's daughter, Poppy, to be erased from existence and causing everyone, even the Doctor himself, to forget her existence, with a distraught Ruby being the only one to remember her. After managing to convince the Doctor of Poppy's prior existence, Ruby implores him to go save her, recalling the time the Doctor once saved her from the Goblins. while Belinda also remembers a time in her childhood the Doctor had saved her from being hit by a car, and also begs the Doctor to save their daughter. With his mind made up, and knowing what he needs to do, the Doctor bid farewell to everyone and left to save Poppy.
Running back inside the TARDIS, and regretfully voicing how much he loved the face of his current incarnation, the Doctor prepares to unleash a wave of regeneration energy in the Time Vortex to rewrite reality and save Poppy. Before he could do so, the Thirteenth Doctor appears, having been pulled from her timeline to help him, and warns him that this event could rupture the Time Vortex, and damage the whole of creation. Knowing her successor's mind was made up, the Thirteenth Doctor prepares to return to her own timeline, before she does however the Fifteenth Doctor says that he loves her, with the Thirteenth Doctor says that she should say that to Yaz, but the Fifteenth Doctor responds by saying that she never did, but Yaz knows. After the Thirteenth Doctor is returned to her timeline, the Doctor willingly gives up his existence in his current incarnation and triggers his regeneration by unleashing his regeneration energy into the vortex and restoring Poppy back into reality. (TV: The Reality War [+]Russell T Davies, Doctor Who series 15 (BBC One and Disney+, 2025).)
State of grace[]
After restoring the timeline to normal, the Doctor woke up in Belinda's yard. With the method to restore Poppy now being irreversible, the Doctor's regeneration was now underway; however, he's able to hold it back long enough to see if his plan had worked. The Doctor is soon greeted by Belinda, who introduces her to Poppy, who despite being restored, is no longer the Doctor's daughter; she was now 100% human. The Doctor also meets Belinda's mother, Lakshmi Chandra. After bidding his final farewell, the Doctor promises that he will meet with Belinda again one day, but no longer with his current face, before departing in the TARDIS. (TV: The Reality War [+]Russell T Davies, Doctor Who series 15 (BBC One and Disney+, 2025).)
The regeneration[]
Not wanting to be alone when he regenerates, the Doctor parks the TARDIS in the vastness of space near the Star of Bethlehem, which was created by the Villengard's star seed and Joy Almondo's consciousness. He declared that being him was an absolute joy before he finally begins to regenerate. Before the regeneration ends, his apparent successor partly emerges and is taken aback at her striking resemblance to Rose Tyler. Still engulfed in regeneration energy, she excitedly says her first words "Oh, hello!" (TV: The Reality War [+]Russell T Davies, Doctor Who series 15 (BBC One and Disney+, 2025).)
