Fall of the Eleventh

You may be looking for Siege of Trenzalore.

Fall of the Eleventh
Type:	Regeneration
First mentioned in:	The Wedding of River Song
First appearance:	The Time of the Doctor
Part of:	Siege of Trenzalore
Location:	Clock Tower, Christmas The Doctor's TARDIS
Result
The Eleventh Doctor becomes the Twelfth Doctor The Doctor receives a new regeneration cycle Destruction of the Parliament of the Daleks and end of the Siege of Trenzalore.
← Previous	Tenth Doctor's regeneration
Next →	Twelfth Doctor's regeneration

The Doctor's regenerations
Timeless regeneration cycle
First Doctor's regeneration cycle
New regeneration cycle
Other regenerations

About the Doctor

The Eleventh Doctor, having expended the 12-regeneration life cycle beginning with the First Doctor, was enabled to undergo what he called "regeneration number thirteen" into the Twelfth Doctor after being provided with additional regeneration energy by the Time Lords at the end of the Siege of Trenzalore. (TV: The Time of the Doctor) This event was prophesied as the Fall of the Eleventh by Dorium Maldovar. (TV: The Wedding of River Song)

However, in a timeline viewed by the Doctor earlier from his perspective, the Doctor was seen to have finally died, with their TARDIS growing its exterior dimensions and acting as his grave. (TV: The Name of the Doctor)

History

Anticipation

According to one account, the Tremas Master claimed that the Valeyard was the Doctor's "penultimate reincarnation… somewhere between [their] twelfth and thirteenth regenerations". (PROSE: The Ultimate Foe)