WOMAN: Forests tend to be naturally spooky places.

They are dense with trees letting in little light and offering plenty of spots for predatory animals to hide while stalking their prey-- prey that sometimes include humans.

But life also thrives there.

For the Slavic people, there's one spirit that rules it all, a lord of the woods, the Leshy.

The Leshy is a shape-shifting creature that may appear human, but also takes on the form of the animals and plants he protects.

He was once believed to lead travelers to their deaths but could also ensure a successful hunt.

He kidnapped young women, but kept cattle from getting lost in the woods.

He was feared, but also revered.

The Leshy isn't just some high-level boss in a video, but an important, mischievous, powerful spirit, that can trace its history back to ancient religious and cultural beliefs.

I'm Dr. Emily Zarka, and this is "Monstrum."

If you've ever been in the woods, you know how scary they can be and how easy it can be to get lost.

In one 19th century text, the Leshy is directly connected to the dangers of the forest.

It reads, "In olden days, when forests were larger and denser "than they are now, the Lyeshy used "to be constantly deluding travelers, and making them lose their way."

And no forest was safe.

While Slavic folklore claimed each forest had its own Leshy, there could be more than one.

Territorial disputes between Leshy were said to be the cause of harsh storms, boulders falling, or crashing trees-- supernatural explanations for real events.

Most often, a Leshy appears in its imposingly tall human guise, with long claws and shaggy hair, sometimes with horns and cloven feet.

He can grow higher than the treetops are small enough to hide behind a blade of grass.

The Leshy's appearance is often inspired by the vegetation of the forest, with bark-like skin and a green beard or hair-- which makes sense, given that his name comes from the Russian word meaning forest.

Leshy translates to wood-spirit or wood-demon.

I had the opportunity to talk to one of my favorite authors, Katherine Arden, who has done a ton of research about Slavic folklore for her Winter Night Trilogy.

KATHERINE: He most often appears as a Russian peasant, but with some slight-- slight oddities.

He doesn't hear a belt.

The left in Russian is associated with the demonic.

So he crosses his caftan left over right.

He also inverts his shoes.

So he wears his shoes on the wrong feet.

He doesn't cast a shadow-- doesn't cast a shadow, and he carries a cudgel or a knout, like a weapon that symbolizes his authority over the forest.

A Leshy may take on a human form and even disguise itself as someone its victim knows.

But it can inadvertently reveal its true nature through small mistakes in their transformation.

And since he can take the shape of anything in his domain, a Leshy may appear as anything from bears and wolves, to domestic cattle, birds, a tree, even a whirlwind of leaves.

A Leshy can also alter its voice.

He might call out to his victims in a voice they recognize or whistle like the wind blowing through the trees.

Animal sounds, the rustle of leaves, and laughter are also part of his verbal repertoire, which he would then use to confuse and tempt the victims.

He was feared because he possessed the ability to lead people and animals astray, forcing them to die from exhaustion trying to find their way home, or misleading them to fall into a ravine or swamp.

Leshy were said to be great gamblers, playing cards against one another and other spirit demons, frequently betting the resources of their particular woods.

When huge populations of squirrels suddenly migrated across the Ural Mountains in the 19th century, some people attributed it to a Siberian Leshy driving his losses to their European kin.

The Leshy received sacrifices and offerings from the people in order to secure his favor and aid in their survival.

As the master and guardian of the forest, a huntsman's success or woodcutter's bounty was believed to be dependent on the will of the Leshy.

Even herdsmen relied on this creature.

Because of this relationship, the herdsmen were seen as intermediaries between the human world and the world of the Leshy, the spirit world.

You could avoid offending a Leshy by respecting the forest, not only in terms of taking resources, but in general modes of deference, like not whistling or swearing, and not intentionally harming plants.

Hunting on certain festival days was also forbidden to avoid the Leshy's wrath.

Laying out the traditional meal for greeting important guests, bread with salt on a tree stump, might keep you safe from the Leshy.

This seems pretty minor, but it was-- and in some Slavic countries, still is-- a very important gesture.

Bread was synonymous with food.

If a household didn't have it, they didn't have the resources to eat.

And salt was a rare commodity, so sharing it expressed hospitality.

Other protections against the Leshy included making the sign of the cross, saying a prayer or spell, wearing clothes backwards or inside out, retracing your steps out of the forest, or making the Leshy laugh.

So while those Slavic folklore describes them as antagonistic towards humans by nature, you can win one over with a little respect.

They can actually seem pretty reasonable in a lot of ways.

Unfortunately, we can't know the exact origins of the legend since there is no record of any Slavic mythology, which was, honestly, a shock to me.

Many scholars agree that nothing about the original Slavic gods, creation myths, or stories of their afterlife has survived history.

The earliest records of the Slavs dates back to only the 6th century.

Around that time, the Slavs migrated into other territories and developed into different cultures.

But one of the things they kept in common is their folklore, including stories of the Leshy.

Its likely oral tradition played a huge role in the stories' early creation.

In fact, "Slavs" comes from the Proto-Slavic slovo , meaning that the people call themselves "those who speak with words."

However, it's speculated that the Leshy was later heavily influenced by Christianity.

As Christianity spread, it mingled with paganism in local folklore.

And there's also a Christian explanation which says that the Leshy and other forest and household spirits were angels that were thrown from heaven after the war between angels.

They fell to earth and became forest spirits.

Or the other one is that spirits like the Leshy are the children of Adam and Eve, born after the fall of man, who went away because they were ashamed and were shamed, and they became spirits of the forest.

EMILY: What was once simply a guardian of the forest became a more devilish figure.

This explains some Leshy traits, like the cloven hubs, which were often associated with evil deities in Christian stories.

And even in some variations of the monster, a Leshy is created from the marriage of the devil and a witch.

Or they could be descendants of Satan's army.

A hunter or herdsman could secure safety and success by creating a pact with the creature, an act that required renouncing Christianity.

In some stories, Leshies were said to appear in military uniform, which may have been inspired by real fugitive soldiers hiding in the woods.

In other cases, the Leshy is said to approach humans around a campfire, asking for food.

The forest did historically serve as a place of shelter for outliers of society.

Perhaps the Leshy asking for food is an exaggeration of such individuals looking for assistance.

Most of what we can study about Slavic spirits now comes from materials recorded in the 19th century, when urbanization and advances in science and education made belief in the supernatural tenuous.

Nevertheless, an 1850's Russian study found that many peasants claimed to have encountered a Leshy personally.

The power of Slavic folklore lasted a long time, and it can tell us a lot about how the Slavs saw the world around them.

The Leshy has become less popular over time, perhaps because the lessons he teaches are no longer as relevant, as the forests have been cleared, and rural Slavic life became less common.

While the rituals associated with the guardian and demon of the forest dwindle, the idea of him does appear in popular culture now and again.

Despite what they may tell you, a Leshy is both a guardian and an adventure.

Since I know you've spent some time over in Russia, and you've done a lot of work with some of these native language texts, do you still think-- or have you encountered people who still believe in the Leshy?

KATHERINE: Definitely had a resurgence with the last like, 20 or 30 years, which is a way of people, I think, to get in touch with their own country, their own history, their own landscape.

Definitely there's a ton of superstition in Russia.

It's probably the country that loves superstition the most of any place I'm traveled.

That can mean unmarried women can't sit at the corner of the table, like walking under ladders, cats, giving bread to your household guardian.

As far as somebody who believes specifically in a Leshy, I haven't met somebody like that.

But I think more people are willing to believe in the power of nature.

So I think believing that the forest has a presence and a life and a divinity, I think is certainly real and alive in present Russia, yeah.

EMILY: Neither good nor evil, this forest-dwelling shape-shifter was scary because it could be lurking around every corner.

The Leshy represents a deep respect for the forest and acknowledges the dangers humans encountered there, especially when it was largely untamed.

It was something that could only be avoided with caution, awareness, and a sincere appreciation of your surroundings.

The moral of the story-- be nice to nature.

You never know when a giant forest spirit will come for you.