Magical people such as trolls, vampires, and nopperabou have had a complicated relationship with nonmagical folk. They were mostly sworn to secrecy, but not everybody followed that oath. Nonmagicals wouldn't have been writing stories about marauding werewolves if it weren't that they witnessed it now and then. Naturally, the incidents of exposed magic lead to speculation, panic, and other reactions from ordinary people, including those who try to seek magical help, or who harass magical folks, or even murder them. Magical creatures get ashamed by stories of their freakiness, or hostility, or simply by being reminded that if even in a small way, their Masquerade malfunctioned. And they have no escape from the dangers of their enemies, who drag their posterity into the fight. They live in fear of being attacked, and eventually it attracts the attention of various governments around the world.
Around WWII era in America, fighting between magical creatures and the plain humans who seek to kill them climaxes beyond what it had been like for years, and politicians in on the secret begin to take action. The Federal government creates a bureau that negotiates with the creatures and the hunters, offering the creatures protection and assisted secrecy, and offering the hunters a job in keeping these dangerous creatures contained. They deceive the creatures into thinking this is a good idea, by keeping their new homes (concentration camps, really) in the appearance and function of your average villages and towns and by keeping restrictions on magic minimal.
The facility I'm focusing on is in central Michigan, with a lake, a forest, fields, and wetlands. It isn't too far in the wilderness, by demand of the guards, and has become closer to civilian districts by having expanded due to population growth. The more dangerous creatures are kept on-site in a building where they are kept drugged, weakened, and away from magical paraphernalia that they could use to escape or do harm; However to keep up the public tranquility, only treason or serial violence earns this punishment. Rarely, somebody might be executed, but execution isn't foolproof.
But propaganda can only control so many people, and only for so long; Any fool knows that, so even before the creatures discuss coming out of hiding there were measures to deter benign escapees. Thorn trees and other environmental modifications are planted around the perimeter to deter escape by foot, horseback, or bicycle. But what's to keep anybody from hopping on an enchanted carpet or turning into an eagle and flying over those trees? How can somebody be kept from wading around the lake's edge, sailing across, or swimming to freedom?
Naturally, some magical people will work with their captors, but magic cannot banish anything that isn't a magical construct (and magical creatures don't count as constructs). It can't be used to completely control anybody's minds, and any compulsions it causes are instantly broken if they're recognized as being magical. It also cannot create large forcefields, or make invisible anything larger than a wagon and a team of four horses.
As well, all magical creatures can cast spells, though some have predispositions towards certain spells. Also, I'm not playing by modern established rules of magical creatures. There are a few distinct "species" like tengu, and hulders. There are no distinct werewolves however, not that a mage wasn't caught transforming into a wolf and began that idea. It's really difficult to explain, so I'm going to describe one of the characters to give an idea of how things work.
Now everybody from the spider on the ceiling to the elf who sells fish has life force, which is tied in various ways to the functions of being alive, and separate from magic. In most creatures, life force is very stable. In some, not so much. Sorin, is what you might call a vampire or you might call a warlock, what his mom would reluctantly call a strigoi, and what Dr. Linden would say is a mage "suffering" from parabiotic hematophagous syndrome, or just parabiosis. This is where, from the first time he tasted blood (in his case, when he lost his milk teeth, but reasonably that happens sooner in some cases) his life force lost its stability. Its levels would gradually drop, and his magic would work in its place. While this kept him alive, it was a very different sort of alive than if his life force was at healthy levels. Usually, it only really leads to crabbiness, malaise, and things falling over at random around him. Drinking blood, whether from an animal or a person, usually fixes this, but if he didn't drink enough blood and let it get out of control, his heart would stop beating, and his bodily functions would basically behave as if he was dead, even though he'd still be up and walking. He'd also get crabbier. This means he'd need to consume a lot of blood in order to stay healthy, and he has really tough kidneys to filter out all that iron. It also means that while it's possible to kill him, he's likely to not stay dead; In any creature, the body retains its magical properties even after death, and with him it's no different, except that his magic can and does fill in for his life force when his life force is lacking. For this reason, vampires have three different life classifications; live, revenant, and terminal. One way he took advantage of his parabiosis, unlike most vampires, is that he had a friend remove his heart and he buried it in a jar somewhere, making it so that fire wouldn't kill him terminally, it would be less likely for disease and toxins to kill him terminally, and it would be more difficult for a spell to kill him terminally. Anybody who knew the location of his heart could burn it and he'd be a goner even if they didn't harm the rest of him. Or if they wanted to get fancy they could use it to channel a curse that could terminate him through other mechanisms, like manually mimicking ebola. A more common side effect of his parabiotic state is that he can't cross bridges without casting a complex spell, and that, at least when he went from live to revenant, he's paralyzed whenever he's in direct sunlight, he doesn't have a reflection. As well, his shadow became almost like a body part; one could pin him in place by stabbing through it; Eventually it developed an infection and auto-amputated; It also isn't uncommon for a vampire's shadow to be forcibly torn off, or to have holes in it. His parabiosis also makes it more difficult to use talismans because the excess magic interferes. Other than that, he's just like any biotypical, so don't don't destroy his kidneys or anything. Those things take forever to reconstruct. I hope this was necessary, 'cause now I feel like I gave this too much attention and detail to even make sense.
