Demons are mysterious creatures and vastly different from each other, there are demons that represent the seven sins and demons that represent death, life and nature. Demons can become patrons to humans who seek magical abilities and can become guests in the bodies and mind of living beings.
If a demon uses a living creature as its vessel it must occasionally bathe in or consume the blood of a virgin to keep the vessel intact. Demons can’t be killed but they can be brought back down to their original domain.
Ghouls believe to have originated in Arabia, no one is certain how they came to be but over time they’ve discovered that some people are born with a tainted soul and will cause a human to turn into a ghoul after death (these people normally die around their 20s and 30s) while some can become ghouls if they eat the flesh of one. Ghouls are often found in cemeteries feasting on the dead. With the rise of Ferrymen and Ferrywomen, the population of ghouls severely decreased. Turnings have gone down but no one is certain who is to become a ghoul until after death.
Vampires are children of the night. They’re creatures that come to be when they have been horribly wronged and that wronging leads to their death. Vampires are noticeably different from humans, they have red lips and red eyes with skin that turns a few shades paler. When feeding their eyes and lips glow. Humans can be turned by vampires but for this to happen the human must drink the blood of a vampire.
Men cannot be turned into vampires by being wronged. Only women. Vampires are also rather seductive and can easily charm others, this normally results in vampires having thralls for protection and feeding.
Not all vampires have issues with garlic but it is common for them to have some sort of allergic reaction.
Read more on vampires here.