Houbin was a large city that was getting ruled by a vampire viscount family of the same name as the city. Any city with a noble vampire ruling over it was going to be somewhat large and that was exactly the case with this city. It was also an important city as a special type of fire could be found in this city.
Vampires were not normally not very fond of fires even though it was not that harmful for them. So they had created a special smithing method in which they were capable of creating various kinds of weapons without involving fire at all.
But this city had a special type of fire that was not uncomfortable for the vampires and instead it was extremely suitable for crafting vampiric weapons. Blood was a very important part of the refinement process of vampiric weapons and the fire of this city was capable of improving the quality of that blood.