Death can come to any character in a campaign, including the time lord. Traditionally regeneration allows them to return to the world of the living, albeit in a new body. However, like the 10th Doctor, some players might be quite attached to their current incarnation and not want to change it just yet.
Luckily the series provides us with various ways to allow the time lord a little more time in their current form.
The easiest way to handle this is to initiate an flashback. As the Time Lord regenerates their mind goes back to adventures that haven’t been revealed yet. Those final moments can seem like an eternity, allowing you to set many adventures in the past.
These flash back adventures can be an excuse to allow the Time Lord to do all the things he wanted to in his current incarnation but never got the chance. Maybe he always wanted to defeat a particular alien race, visit an historic period or see an old friend one more time.
It can also give the player time to think about what he wants his next incarnation to be like. These flashback adventures can highlight what his current incarnation is poor at and what he wishes to be better at.
There is also precedent for a Time Lord basing his next incarnation on someone he has met in the past. There maybe an NPC in these flashback adventures that the player takes a shine to and adopts the personality and appearance of when they do regenerate.
Taking the approach of ‘The Impossible Astronaut’ the Time Lord might regenerate or even die only for a younger incarnation to join the companions, perplexed at why they are so upset.
They will then know what fate has in store for him and even what his next incarnation will look like. For the moment they can still travel with the younger incarnation before he drops them off (maybe to reunite with the newly regenerated incarnation) and picks up their younger selves to accept his fate.
‘Journey’s End’ revealed that if a Time Lord has a compatible organic mass he he can syphon off his excess regenerative energy. In effect his physical body is healed at which point the regeneration energy is expended regenerating the organic sample, in this episodes case growing an entire body from a severed hand.
This requires more preparation, since a body part must be removed. The 10th Doctor was lucky that his hand was removed during the period in which his body was still healing. Still, the knowledge that they can retain their current incarnation for a little longer might be some comfort for a Time Lord who loses a limb and remembers to retain it.
‘Let’s Kill Hitler’ demonstrated that a Time Lord (or at least a human/time lord hybrid) can sacrifice some (or all) of their regenerations to heal another Time Lord without triggering a physical transformation.
In a game with multiple Time Lords this can be a good way to strengthen the bond between characters. Within the fiction of the game the sacrifice of a regeneration is huge but in actual fact with each character starting with 13 regenerations they have plenty to spare and are unlikely to use them all during a campaign.
It has been indicated that a TARDIS can help in the regeneration process. It is feasible that if a Time Lord can get to their time ship in time they could regenerate into an identical version of their current incarnation. They’ve still lost an regeneration but determined how it will appear.
In ‘The End of Time’ the Doctor is able to hold on to his 10th incarnation for quite some time after his body has initially been healed. On screen he visits Martha and Mickey, Sarah Jane Smith, Jack Harkness, visit a book signing by Verity Newman and Rose Tyler. In the Sarah Jane Adventures episode ‘Death of the Doctor’ it is revealed that he looked in on many more of his companions.
This all indicates that the 10th Doctor held of regenerating into the 11th Doctor for weeks, months or even years. Quite a feat for what is usually a quick, traumatic process. It could be that after a certain number of generations a Time Lord can delay the process or stop it entirely, just as the Master does in ‘Last of the Time Lords’.
If a player is particularly attached to this incarnation you may allow them to delay their regeneration in this way. The drawback should be that if they are fatally injured before they regenerate then they will die, since they are prevent the healing process.
This will keep the spectre of death always in the mind of the Time Lord. They know they always have the choice of letting their regeneration take its course or dying forever. This may make them a little more cautious in subsequent adventures.
Used temporarily it can serve the same function as the flashback suggestion above, allowing them to tie up loose ends. This can lead to a very effective ‘Farewell Tour’ story arc, with their regeneration getting ever closer (the Time Lord might start to shimmer gold if they get stressed or catch glimpses of their future incarnation when they catch their reflection).
A Time Lords refusal to let go of their incarnation could be contrasted with non-Time Lord player characters or NPCs dying. They have no extra lives which should put the Time Lord’s squandering of his life in perspective.
Incidentally this does open the door to the possibility that the 3rd Doctor could have had a great deal more adventures on his way from Metebelis 3 to UNIT HQ. These could be explored in adventures or used as a mystery, especially if the 4th Doctor forgot these events due to the strain his body was under.
I doubt he held off the regeneration for years, probably at least a day maybe a week