Rose not only witnesses the destruction of her planet but realises that her mother and everyone else she knows will die and from her viewpoint in the future have been dead for a long time.
The Doctor is able to speak about the end of his home world and his people. This seems to inform his viewpoint as he lets Cassandra die. It is his inaction that allows her to dry out. He points out to Rose that everything dies, just as humanity lets Earth be destroyed because its time is past.
Time travellers are drawn to the momentous occasions in time. Chief amongst those, besides important historical events, are beginnings and endings. PCs can be there when time runs out and the curtain finally falls.
This episode shows the end of Earth (although not the end of humanity) but there are plenty of other planets in the universe the PCs can be on hand to witness. Skaro is destroyed in ‘Remembrance of the Daleks’ (maybe) and Mondas exploded in ‘The Tenth Planet’ but there could be more to learn about those worlds final moments.
It is important whether the adventure is built around the PCs trying to survive the cataclysm that ends these worlds or whether they are just there to witness them (from the safety of a facility like Platform One.)
If they are just there as witnesses who else is present? Is there a mood of mourning or celebration? Will anyone try to save the world?
An adventure could be based around the end of a race. What is the ultimate fate of the Daleks, Cybermen, Ice Warriors, Draconians and others? Do they wither away, do they redeem themselves, do they change completely into a new race?
The PCs might learn that an evil eventually becomes a force for good or is vital for the survival of the universe. This will forever prevent them from being tempted to wipe out the race before they can achieve their destiny.
The danger is if the PCs learn too much about a races future they will fear altering their history. They might hesitate in thwarting there plans in case this failure will divert them from the fate.
PCs might decide that it is there destiny to put the aliens on the right track, pushing them towards the future they’ve seen. This can be an ongoing project, with them steadily improving the alien race.
They could learn that a currently friendly race will betray the rest of the universe or will create a dystopia. In this case they might not know how they change from the good beings they know to the terrible creature they’ll become. This can be a source of tension as the PCs keep waiting for the change to occur.
Witnessing the end of a race can let the PCs take stock of everything they’ve done. Having this knowledge can be a great burden, especially when they meet the race in the past. Do they keep it to themselves? Do they warn them or do they goad them with the knowledge?
It can be startling for the PCs to realise that past that point in history they will never encounter that particular alien race. Whatever happens to the universe next will happen with out them.
On a smaller more personal scale the PCs could witness the end of a NPC close to them or just find evidence of their death (like a gravestone). Intellectually they knew that the NPC would eventually die but to come face to face with that fact can take them by surprise.
Witnessing an ending can be a real test for a time traveller. It can be challenge not to try and go back and change it or prevent it. The lesson of ‘The End Of The World’ is that sometimes you just have to accept it.
This sentiment is repeated in ‘Father’s Day.’ To try to prevent an end is to pervert the natural order of things. It is terribly sad but not even a Time Lord can hold back the hands of time.
The important thing is that life still goes on. Even with Earth gone humanity is thriving. They even create Earth II. Every ending is just another beginning in disguise.
How PCs react to endings can be very important to the development of their character. It could even be a test by the Time Lord, to see if they are the type of companion who will accept the web of time or try to change things.
The PCs might find themselves in opposition to someone who won’t permit something to end, whether it be their own life, someone close to them or their planet. The PCs could seem like monsters to this person, championing death while they are struggling to see life continue.
Here the PCs try to prevent stagnation or the development of the universe being stalled. This is particularly effective if they know what comes next.
A particularly morbid group of time travellers might make endings their specialty. They make it their business to witness the death of historical figures first hand, to be there when empire crumbles, when planets are destroyed and races become extinct.
The PCs might take this role or they could encounter a group of misery tourist time travellers. The outlook of such time travellers would be very different to most Doctor Who groups.
The greatest gift of a time traveller is that the end doesn’t have to be. In ‘The End of the World’ the Doctor and Rose can witness the destruction of Earth and then travel back to the 21st century, surrounded by people and search for fish and chips.
This knowledge prevents a campaign from become too depressing. Everything has its time but the PCs have all the time they’ll ever need.