Vanir

In Norse mythology, the Vanir (singular Vanr) are a group of gods associated with fertility, wisdom and the ability to see the future. The Vanir are the namesake of the location Vanaheimr (Home of Vanir). 
The Vanir are attested in the Poetic Edda, compiled in 13th century from earlier traditional sources; Prose Edda and Heimskringla, both written in 13th century by Snorry Sturluson; and in the poetry of skalds.
All sources describe the deities Njöror, Freyr and Freyja as members of the Vanir.

Dean says:

Vanir were Norse gods of protection and prosperity, keeping the local settelements safe from harm.

Villages built effigies of the Vanir in their fields. 

Other villages practice human sacrifice; one male and one female.

This particular Vanir, it's energy sprung from a sacred tree.

If the sacred tree tourched, it will kill the god.

Shapeshifter

Every culture has a shape shifter lore. Sometimes they are myhthologic creatures sometimes a fairy tale character. They has ability to deform and form into another. They are alike futuristic killing machine T-1000. They can figure animals or different kinds of living things. All the diffrent lores says the same: that they can only be killed by silver bullets. 

The Supernatural Tells us:
Animals can have a sharp sence the paranormal.
A lot of cultures bealive a photo can catch a glimpse of the soul.
A shapeshifter is some kind of a dark double of a person look like the person but it isn't (like a doppelganger).  That explains, how a person could be in two places at once.

It doesn't just look like you, it would be you or it will become you. It's like, it's downloading all your memories, thoughts... Like the Vulcan Mind Meld. 
So it won't kill it's victims on the spot. It would need them to be alive for keeping the psychic connection.

Evoluation is about mutiation, so maybe this thing was born human but was different. Hideous and hated. Until it learned to become someone else. He is all alone, close to no one. All he wants is for someone to love him.

Every culture in the world hass a shapeshifter lore. Legends of creatures who can transform themselves into animals or other man. Skinwalkers, werewolves...

When the shapeshifter changes shape, maybe it sheds.

  

No matter what kind of shapeshifter it is, there's one sure way to kill it:
Silver bullet to the heart.

Wendigo

The Wiki Tells us:
Wendigo (other names; windigo, weendigo, waindigo, windago, witako, windiga etc.) is legend creature of Algonquian people (a Native American tribe). 
It is cannibalistic, another way to describe is that he eats human. Lore says it's a spiritual being and it can possess people.
And according to another description it was once human, in time it has began to eat human flesh and it has changed into the creature it is.

The Supernatural Show Tells us:
Moves too fast to see and hide well too. The claws, the way it can mimic a human's voice... it's damn near a perfect hunter, it's smarter than avarage human. This thing is a good hunter at day but unbelievable hunter at night.

Anasazi symbols for protection, wendigo can't cross over.

"Wendigo" is a Cree Indian word. It means "evil that devours". 
They are hundreds years old.
Each one was once a man.
Sometimes an Indian, or other times a frontiersman or a miner or a hunter.

How's a man turn into these things?
Well it's always the same story.
During some harsh winter, a guy finds himself starving, cut out from supplies or help.
He becomes a cannibal to survive, eating other members of his tribe or camp.

Cultures all over the World believe that eating human flesh gives a person certain abilities:
Strenght, speed, immortality...
If you eat enought of it, over years you become this, less than human thing. 
You are always hungry.
More than anyting, a wendigo knows how to last long winters without food.
It hibernates for years at a time.
When it's awake, it keeps it's victims alive, it stores them so it an feed whenever it wants.