‘Kill The Moon’ reveals that the moon is actually an egg, containing a vast winged life form. This comes as a surprise to everyone, including the Time Lord. This knowledge could have an impact on your own campaign.
Firstly the Doctor believes that this species is unique and that in 2049 it is the last of its kind. The Doctor is probably basing this on the fact this is the first time (on television at least) that he has encountered a creature of such scale that it could be mistaken for a moon and since he is so well travelled if they were more common he should have encountered more by now.
This doesn’t necessarily have to be true, since it is a big universe. Indeed the Doctor is only just now finding out about these events but if they were part of the original timeline then it would be common knowledge and could have been discovered during any of his previous visits to any period after 2049. Just because the Doctor doesn’t about something shouldn’t automatically mean it is rare or obscure knowledge.
What we are presented with is a creature that takes a hundred million years to hatch, weighs 1.3 billion tonnes when it emerges and can lay another moon. This is pretty extraordinary and leaves lots of questions.
Harking back to the question of ‘what came first, the chicken or the egg?’ where did the first moon come from? Was there a moon 100 million years ago or did this one happen to come into orbit of our planet from elsewhere? Did the emergence of the previous moon dragon or the arrival of this one’s egg influence the Silurian’s decision to hibernate or the ejection of Mondas from our solar system?
The disaster on Earth is caused by the extra weight of the moon but if it has always been growing there why were the effects of its mass only felt in 2039? Eggs are a closed system and usually get lighter (as moisture evaporates) rather than gaining more weight as the baby is formed. What happens here isn’t normal.
It could be that growing space dragon is actually in another dimension, the moon just acting as its anchor point and eventual gateway. Thus until 2039 there is only the outer shell of the moon to exert an influence on the Earth.
The natural disaster occurred after a Mexican mining survey. It could be that in breaching the outer shell of the moon they caused the barrier between dimensions to breakdown, allowing the space dragon into our dimension. Only then does its mass cause an effect on Earth.
We might also question how the space dragon laid another egg. The implication is that this new moon will also eventually hatch which would require a form of asexual reproduction. Parthenogensis does occur in several species so isn’t impossible although it does obviously keep the genetic pool small.
As indicated above an egg is a closed system so the question remains where the space dragon got the mass to create another egg. Since it lays the egg after it hatched it is possible that part of it might be gained by recycling the disintegrating shell but that leaves a lot of mass unaccounted for.
The Doctor notes that the moon dragon is feeling the sun and getting warm after it has hatched. It is conceivable that it is converting that solar energy into mass and maybe that it was also able to gather solar rays through the shell of the egg. This still seems unlikely.
If the dragon does grow in another dimension it might mean that there is other mass there that can be converted. It could be that there are more moon dragons in the other dimension, along with planetoids. Rather than a new dragon growing it simply takes 100 million years for them to pass through the gateway, bringing with them the anchor for the next of its species to follow. In effect this would be a very slow invasion of our dimension.
The Earth is compared by the Doctor to a nest for the moon dragon. A nest is usually something constructed to protect eggs. Is the Doctor implying that the moon dragon or another species built or designed the Earth to protect the moon?
What protection could Earth have provided to the moon? It is possible that the Silurians, who were capable of space travel, might have been able to intercept any threat to the moon if they hadn’t hibernated but humanity wouldn’t until the late 20th century.
It is possible that Earth would act as a decoy? By placing the moon in close proximity to a more resource rich planet the hope is that it will be overlooked. This also means that when beings like the Doctor protected the developing world they were in turn protecting the moon egg.
A more horrible scenario is that the Doctor isn’t correct. It would be far more likely that the Earth would act as a food source. In a darker take on this story PCs could have to deal with a ravenous predator of unimaginable scale devouring billions before flying into space.
The status quo is just about restored at the end of ‘Kill The Moon’, with Earth having a new moon but what happens now to the moon dragon? Where would it go now and what would it do? Would it lay any more moons?
Such a beast could have enormous tactical value. Any number of species might try to capture and place it under their control. Certainly psionics or cybernetic technology could allow someone to control a moon dragon. PCs could be faced with the challenge of dealing with a moon dragon that has been turned into a biological weapon.
There is also the question of what happens when the moon dragon dies or is killed. PCs could encounter civilisations living within the hollowed our corpse of a moon dragon or looters stripping it for organic parts. Some species might convert it into a dragon shaped spaceship.