RTF is a global modification that replaces all towns in the game.

Why, for example, wouldn't you add a skill that allows werewolves to transform into their werewolf form as the third upgrade for vampires? (You could tell a story like this: vampires, fascinated by eating their own kind, and after drinking dark Necropolis blood, mutated into these werewolves.

Please explain for beginners where and what to change; I'm not very familiar with this. And where to put it.

Added 1 minute ago
I have no idea how to change the zip file for the pack.

You did something wrong; when you take this blood without a mod, it immediately gives 500, and until it's removed, no damage is dealt. I tested the blood; there's no health, the blood should give them additional HP, I think.