Vitae uses?

[Niky]

I heard people saying there are multiple NPCs that trade Vitae for usefull itens, but so far I only found the one who trade it for extra bullets.
Are them supposed to be to the south? Because I am pretty sure I explored what I could on the north portion of the map (I have no keys :c)

(ALSO, I did not know the First Knight was supposed to be the hardest one, killed her after 7 tries, I ended up with 1 HP)

[Pugware]

You didn't explore all you could, first floor first right has the most important npc.