Thirteenth Doctor's regeneration

"Tag, you're it."

- The Thirteenth Doctor's last words

Having been mortally wounded by the Qurunx's destruction beam after it was redirected towards her by the Spy Master, the Thirteenth Doctor underwent her regeneration into the Fourteenth Doctor whilst standing on a cliff just outside of the TARDIS. (TV: The Power of the Doctor) This regeneration was part of the Doctor's new regeneration cycle. (AUDIO: Salvation)

Anticipation
After the Flux, Time hinted at the Master's Dalek Plan and warned the Doctor, "you won't outrun me. Your time is heading to its end. Nothing is forever. No regeneration, no life." (TV: The Vanquishers)

After Yasmin Khan expressed her attraction to the Doctor, the Doctor said that she couldn’t get into a relationship because “time always runs out”. The Doctor later asked Yaz to try to live in the present of what they had while they still had it, and made a wish on a skipping stone that it could last forever. (TV: Legend of the Sea Devils)

Now anticipating her regeneration, the Thirteenth Doctor wrote a book about all of her lives, also using material written by other incarnations from the past and her fam, to aid the new Doctor if they "[felt] weird" after regeneration. (PROSE: A Short History of Everyone)

Causes
At the end of the Master's Dalek Plan, fatally wounded the Thirteenth Doctor as revenge for the reversal of the Thirteenth Doctor's forced regeneration. (TV: The Power of the Doctor)

Regenerative process
Coming to a cliff, the Thirteenth Doctor regenerated. This regeneration involved large spouts of golden regeneration energy which had an electrical crackle. (TV: The Power of the Doctor)

Aftermath
Immediately after the regeneration, the Fourteenth Doctor got involved in an adventure at the Dalek Dome. (COMIC: Liberation of the Daleks)

Theoretical regenerations
During the Thirteenth Doctor's life, the possibility of regeneration was discussed for several situations prior to her actual regeneration.

While facing being shot by guards of the Good Doctor, she said any attempt on her life would result in a "miracle". (PROSE: The Good Doctor)

Trying to generate enough energy, the Thirteenth Doctor once considered regenerating and using residual artron energy. (PROSE: The Maze of Doom)

During the Redaction, the Doctor remarked to Cleo Proctor that she would stand up again if she "clobber[ed]" her, remarking that she would regenerate "Possibly several times" and then "who can say?" as to how many times. (AUDIO: Salvation)