Vrykolakas, or simply vryks are monsters first described in Greece. They are similar to Vampires in many ways, particularly the breed Revenants, but with a number of notable differences that exclude them from that categorization, mainly that they feed not on blood, but on flesh. Their appearance is nearly identical to those of revenants: bloated, ruddy skin, with the exception of the fact that they grow crooked, dog-like teeth and sometimes claws and fur, similar to the berserker form of the werewolf.
They are not individually as powerful as most Vampire breeds, being incapable of any form of shapeshifting or invisibility, traits common to nearly all Vampires. However they are very fast and strong at full strength, and can reproduce quickly throughout a human population if it desires to, capable of infecting entire towns in a matter of weeks if left unchecked.
After an Alpha vryk arises, the infection spreads quickly to those it attacks and bites, similarly to how Vampires spread. However, the Alpha, rather than having been infected by another vryk, is instead a person who, in life, either was a werewolf, or received a minor exposure to lycanthropy, such as by eating an animal that was killed by a werewolf, an action that would not, on its own, transmit the full lycanthropy. This Alpha very holds a certain power over its pack, in much the same way alpha werewolves usually do, and often retain more of their intelligence than their apostles do.
Vrykolakas are, generally speaking, less durable than their vampire cousins. For the most part, similar procedures are needed to ensure their death, especially for the Alpha, however there is slightly more leniency in the execution of those requirements. For instance, severely damaging the brain or neck may be enough to count as decapitation without literally taking the head off. Also, the obsessive-compulsion present in some breeds of vampire definitely takes effect in the beta vryks, and most likely in the alpha, forcing them to count any collection of seeds, rice, or other numerous small implements presented to them, and meaning they can be deterred by most of the same wards and apotropaics as vampires.