Lycozompire

In the fantasy story that I'm working on at the moment, a world called Neverdawn is home to vampires, werewolves and zombies, who have been exiled from that universe's version of Earth. In the absence of humans or other living creatures to prey upon, the undead monsters begin to turn on each other, leading to a centuries-long conflict that only ends after all of them have been transformed - due to all three species' habit of biting people - into an unholy combination of vampire, werewolf and zombie. After that there is no reason to keep fighting as they are all, essentially, the same race.