"He wished he could believe that the Doctor knew exactly what he was doing, but he was beginning to suspect that the fellow just did whatever occurred to him, whenever it happened to occur."

'My people constructed huge bowships that could fire massive stakes made of incorruptible metal through the enormous black hearts of these creatures. The mistake we made, because fundamentally my people are very lazy, was making these bowships intelligent.

'Intelligent?' repeated MacFarlane. 'Is that even possible?'

'Everything is possible in an infinite universe. But yes, artificial intelligence is a thing. Not necessarily a good thing, though as we found. Some of the bowships refused to cooperate, and some went rogue. Some unionized, and refused to attack any Great Vampires without adequate compensation and guarantees of survival. And some developed ways of dealing with the Great Vampires that we hadn't anticipated. That, I'm afraid, is what we're dealing with here.'

DOCTOR: It's always premature to declare victory. There's always someone or something to carry on the fight.