I grew up in Illinois. At that time it was still possible for me to go to places like Dixon Mounds and see Indian/Native American burial sites and learn a lot about the people who lived here before I did.
I get that these were people and we were walking through their graves, but we were learning about them at the same time and that in my mind was much better. Whatever the case it left me with a life long fascination with the native people of this area.
The Algonquin (and Illiniwek) people had a great mythology and SOOO under utilized in games or novels. One creature that I always was fascinated with was the Wendigo. Yes. The Wendigo has been seen a lot in horror fiction, especially with the rise in popularity of werewolves and zombies. But they are still very interesting. The most famous one of course is The Wendigo by Algernon Blackwood, followed by August Derleth's Ithaqua.
This is a creature that possess humans under conditions of extreme cold and hunger and gets them to become cannibals. Also people that engaged in cannibalism were also at greater risk of possession.
The Wendigo is a spirit most times, unable to physically manifest in the world or interact with it. That is until someone in a cold part of the world begins to despair and go hungry. There are plenty of places in the world that are cold and these have hungry people, the Wendigo though chooses someone though that has or will resort to cannibalism to stay alive. Once this is done the Wendigo has access to the victim's heart.
With their heart frozen the victim becomes the physical Wendigo. They appear lean and gaunt, but taller; as if stretched out. Their hands become claws with vile blue talons. Their entire appearance becomes more feral. They appear to be something akin to a ghoul or even a starving were-wold mid transformation. Their are constantly hungry, eating all the flesh they can though they never eat their fill. Eventually the wendigo strains the host body too much and they die completely in a number of weeks. Though there are rumors of giant wendigo, whose head reach the clouds that are thousands of years old.
Armor Class: 3 
Hit Dice: 8d8+4* (40 hp)
No. of Attacks: 2 claws / 1 bite / breath weapon
Damage: 1d6 / 1d6 / 1d6+3 / 1d8+5 (cold)
Special: breath weapon, fear, low-light vision (120’), scent, immunity to cold
No. Appearing: 1
Saves As: Fighter 9
Alignment: Evil (Chaos)
The wendigo is completely immune to all cold based attacks. It attacks with it's claws and bite and can emit a blast of freezing cold air up 4 times per day (save for half).
This demon shares a number of characteristics with were-creatures and undead. A cleric can turn one as a Special Undead. Once a person is infected with a wendigo they can not be cured.