Brief History
There is three moons that cycle the world, two small grey ones and one large yellow one. The moons have a 96 day cycle where all 3 are in the sky, which gives lycanthropes a power surge.
~100 years before current day, The Apocalypse of the Moon ended.
The Apocalypse of the Moon was when Wynshina created a powerful lycanthrope werewolf that took the world like a plague. These werewolves were bigger, faster and stronger than previous werewolves, she created a type of werewolf that took over the infected, and lost themselves when the curse takes hold of them. These werewolves are 9 to 10 feet and weight between 500 and 700 lbs and are berserk. Each of the mortal races had to fend off theses blights in their own way. When the other gods caught wind of this happening, they locked away Wynshina; which she swelled with divine power from her influence on the mortal world. The Apocalypse of the Moon lasted for hundreds of years and only 100 years ago mortals killed enough of the werewolves to where they became just a monster out in the wilderness and not snuffing out all life.
Lycanthropy:
The Goddess of Madness and the Moon, Wyshina; created werewolves to destroy the mortal realm and grant her power. Half-humans & humans highly susceptible to lycanthropy higher DC for contracting lycanthropy; ELVES CAN’T GET IT, no souls.
Demons:
Demons are parasitic, can manifest on the material plane, they have to use mortals souls to infect and use the soul as a power source to bring them from the Abyss. Demons need a power equivalent to themselves or greater to bring them to the material plane. When enough demonic corruption affects the area, it will suck that into the Abyss, almost like the universes fail safe for keeping the demonic invasion of the material plane.
Demons can't cross to the material world easily. It takes very powerful magic to get their true forms here, i.e. balor, guristos, nafsheneen, and other classes of demons. But they can infect, and posses a mortal, putting their chaotic claws into the soul of a mortal and use it to manifest it's true form from the Abyss. Some demons can't do this, bigger ones, higher class demons, but the lower level ones it's easier, it would take a powerful individual to summon a powerful demon. CR for CR. This act shatters the soul of the mortal destroying it, utterly, where nothing short of a Wish can bring their soul back.