Level 15

This hidden feature is exclusively available in the latest Vampirism 1.5 versions for MC 1.12. It will not be included for MC14+.

How to reach level 15

Both vampire and hunter player can reach level 15. The respective way of doing so is unknown however.
However, these hints from a challenge related to this may help you:

Let's play a game, shall we? First to reach level 15 vampire (or hunter) will be featured as an advanced vampire (or hunter respectively). So vampires grab your cloaks, hunter put on your hats and try your best.

I feel like many modern day vampires lost their interest in fashion. Just can't take them serious if they run around in T-Shirts. Same goes for vampire hunter, haven't seen anyone dress up as fancy as Van Helsing in a long time.

https://twitter.com/maxanier/status/1150534967262416899?s=20

Kind of unfair that only players seem to be able to level up. Poor NPCs

oEkesnbsicdrtn rpapae ot aveh knuownn efectsf

Unfortunately I do not know what this means. I got the note from an old friend who traveled another world. She brought back a lot of strange materials, but died of her injuries before being able to explain me what to do with it

https://twitter.com/maxanier/status/1151032974231523328?s=20

I just stumbled upon a difficult math problem. Maybe somebody can help me. 5 + x = 6