The word monster is generally used to describe a being that isn’t human, demi-god or celestial. Having a blanket term for these beings springs from the hunting tradition – anything that kills humans, is a monster. Demons are regarded as monsters, but are in many ways an entirely different issue and won’t be addressed here.
Simply classifying all monsters as evil or bad would be an extreme simplification. Many of the beings are born human and turned into monsters one way or another, and in some cases even cures exist. Some beings are born to be what they are, but might have a choice in the modern world to not follow their natural urges and live life differently.
Of course some types of monsters are by their very nature unable to be anything but dangerous and harmful. The risk that a monster turns homicidal is always there, no matter how much control it exhibits. This is why from a hunter’s point of view things are mostly kept black and white, even when in individual situations they might be far from it.
Many of the beings live at least abnormally long if they aren’t practically immortal, with the exception of werewolves and other monsters who’s being isn’t dramatically altered from that of a human. All monsters have at least supernatural strength, and many have other capabilities as well which mostly have to do with their way of feeding or defending. As a rule all of the monsters can be harmed and killed one way or another. That way might be easy or not.
A Brief history of monsters
This information is not something that player characters know all about, unless they are very well informed on rare lore. It’s here to give an idea about the game world.
The very first monsters, the leviathan, pre-date angels, humans and even souls. God created the leviathans as the first beast to roam the earth, but they turned out to be too ferocious. So God created Purgatory to keep them, and to be the place where all other monsters would eventually end up after their earthly existence came to an end.
Not all the origins of monsters are known, but many are descendent from old bloodlines which have evolved since, created by God or other extremely powerful and ancient entities. One of these examples are the vampires, who all spring from the old alpha vampires. These were created by Eve, a supernatural being whose origin is partially obscured, but who precedes humanity and entered Earth through Purgatory. Vampires were amongst her first children, and it’s entirely possible that a number of the early monsters spring from her.
Monsters have coexisted with humans from the beginning, and they have hunted each other just as long. There has also been, and still is, peaceful coexistence of some kinds of beings and specific cultures or individuals.
What monsters exist in this world?
Basically everything that appears in folktales, myths and religions. Things that are not modern pop culture creations, but have a foothold in tradition. Their representations in this world aren’t the same as in (other) pop culture, and usually just exhibit some of the characteristics that can be recognized in the tales told about them.
See Fandom Wiki to find out how some of the monsters are represented. Any beings not described by the show are re-imagined for the game by people creating it.