Personal History Killer
From Tardis Wiki, the free Doctor Who reference
Personal History Killer was the name given by Bernice Summerfield to an entity found on Morvalvian by Leif Larsson.
Larsson discovered that the entity was capable of rewriting history. He brought it to the Braxiatel Collection in order to rewrite history in favour of the Fifth Axis.
The entity did not like sad stories. While on the Collection, it encountered Peter Summerfield and told him stories. When it realised that Larsson wanted it to write sad stories, it destroyed him and restored the original histories. (PROSE: Fluid Prejudice)