Perhaps if there is a kill/no kill choice for something like this, you could get two things
- By not killing him you get more vampire suck range, or maybe when you spit something out it homes in on an enemy? It could be from him giving you a gift from one vampire to another.
- By killing him you get a shop there - and maybe a special item, like a grappling hook because the shopkeeper has no need for it now that he is up there in the lair - perhaps with a zipline down?
Really this seems like it would come anyway for the game (at least a fight with some vampire, where you would have to fly out of the mouth or something), it is just nice thinking up hypotheticals to this cool game