War Doctor's regeneration
From Tardis Wiki, the free Doctor Who reference
The War Doctor, who himself regenerated from the Eighth Doctor, (TV: The Night of the Doctor) met his regeneration into the Ninth Doctor within his TARDIS, having felt his body "wearing a bit thin" after working with his other incarnations to end the Last Great Time War by relocating Gallifrey to a pocket universe. (TV: The Day of the Doctor) This was the ninth regeneration of his first regeneration cycle; as the ninth incarnation generally did not identify as the Doctor, the so-called Eleventh Doctor was technically "number twelve". (TV: The Time of the Doctor)
According to another account, the Eighth Doctor regenerated into the Ninth Doctor after using the Moment to destroy Gallifrey Original. (PROSE: Doctor Who and the Time War)
