Vampirism is a prominent mod created by the developer Maxanier. It allows players to either become a vampire or vampire hunter in the world of Minecraft, as well as adding NPCs from both into the game.
Both sides have their own leveling systems, hunters level through research and contacting trainer NPCs whilst players who are vampires level by using blood and ritual magic through altars primarily. Obscure lore is also scattered throughout the world in the form of books written in Latin or Scandinavian that require translations to decipher. Players on both sides may also capture villages by right clicking on beacons, either claiming them if they were neutral or capturing them in a battle from the other side.
In a coming update, both sides will soon be able to trigger sieges by killing either NPC vampires or hunters carrying banners that are found wandering throughout the generated world where this mod has been installed. More detailed lore will also be coming in the new books and journals soon to be released as to the nature of both sides.