In ‘Nightmare In Silver’ Mr Clever (the cyber planner Doctor) correctly identifies that the Doctor has been deleting himself from databanks (including those of the cyberiad) but that his absence from the information would allow someone to work out that he existed.
In other words the Doctor had removed himself without replacing his role in historical records. There was no one to take responsibility or credit for the things that he did. If someone was able to see the pattern they’d be able to discover that someone was making a habit of saving worlds throughout history.
The Doctor admits that it is a good point and that he’ll have to do something about it. We never see this onscreen but there are enough gaps suggested during ‘The Name of The Doctor’, ‘Day of The Doctor’ and ‘Time of The Doctor’ for this to occur.
It is no longer enough for the Doctor to simply delete any mention of him, he now has to fabricate false accounts to attribute his actions to someone else. There are various approaches he could have taken that can impact upon a campaign.
The simplest route is to make it seem as if those involved in those events did more than they actually did. This can seem more natural, although it could inflate the legend of the participants but since these would be alterations to historical records there should be little impact on those people’s lives during their lifetime.
This could complicate things for other time travellers who expect more from historical figures. PCs might find that the famous NPCs they met don’t live up to their legend and that the Doctor was actually responsible for their great deeds (and the Doctor frequently claims to be responsible for the triumphs of historical figures anyway).
An advantage might be that time is harder to sabotage because attacking or hindering historical figures won’t prevent major events happening because the Doctor was the actual reason things occurred.
The Doctor gives all the credit to his companions, since there would be documented evidence of their presence it would be simple enough to suggest that they were the ones that saved the day.
The Doctor might see this as a fitting tribute to his old friends, a way to thank them for their support. On countless alien worlds people would celebrate his companions without their ever knowing.
This could be interesting for former companions to discover, either finding themselves travelling to other planets once again or receiving visitors from distant regions of the universe.
The greatest danger is that just as enemies of the Doctor used to seek him out his companions might now be targets. Once they leave his company they will be more vulnerable, sitting targets stuck on a single planet and time zone.
The well-meaning actions of the Doctor could force them to go on the run (possibly banding together). A campaign could be based around former companions escape those who want revenge or around the Doctor trying to protect his friends.
If the Doctor doesn’t want to put anyone in danger he might invent a person to take credit for his actions. This could be different for each adventure he is rewriting or the same larger than life hero across several exploits.
This would be a good opportunity to see how the Doctor’s mind works. What kind of hero does he think could stand in for him without being to much like him? Just how imaginative is he?
You might use this as an excuse to re-tell existing Doctor Who stories with the PCs taking the role of the fictional heroes that the Doctor is using to cover his tracks. They could each represent some facet of his personality.
In the ‘real world’ the PCs might begin to hear tales of the fictional character that the Doctor has created. The PCs might want to seek him out, only to find mounting evidence that he doesn’t exist. How long would it be before they discovered the truth?
The audio ‘The One Doctor’ demonstrated that there are unscrupulous people who are willing to take credit for the Doctors actions. Equally there might be those who seize upon the legendary figure he creates and play that role themselves.
This could be the basis for an adventure for the Doctor. How does he react when he encounters the person he made-up? Would he wonder if he unconsciously had heard or met the person before? If he knows they aren’t who they say they are how does he expose them without revealing the legend is fiction?
The Doctor could seek out others who could fill his shoes. By collaborating with potential heroes he would ensure that they knew what was happening, were able to defend themselves and potentially use the reputation he would be creating for them to do some good.
This would be a good way for original PCs to have a head start. Presumably they’d have done something impressive for the Doctor to consider them but even though their adventures were just starting people would already consider them great heroes.
While this could ensure co-operation from authorities and adulation of fans it also gives them a lot to live up to. Can they convince people that they did all the amazing things that the Doctor did?
They’ll also have to watch out as all the Doctor’s old enemies would now have them in their targets but then isn’t that what they signed up for?
You might also decide that the Doctor would recruit old friends, who have proven ability. This could lead to a group of previous companions that would act to maintain his legend. Possible candidates include Captain Jack Harkness, Ace, River Song and Madame Vestra (possibly with Jenny and Strax in tow). The Doctor could find a way to provide them with their own time machine.
There Is No Doctor
For the ultimate twist there never was a Doctor. He is simply the fiction that your PCs have used to cover their own tracks.