House of the Dragon and Game of Thrones fans know that Westeros is a terrifying place to live. 

Around every corner in the Seven Kingdoms, there are horrors that would reduce even the bravest of knights and boldest Targaryen Kings to tears. Kids have been butchered, dragons fought, and the undead have marched across the realm (well, The North, at least).

Yet, as scary as the Dance of the Dragons and War of the Five Kings were, they’re hardly the creepiest things lurking in George R.R. Martin’s imagination. Yes, the Known World (we’re not calling it Planetos) is a big place, and in the shadows lurk mysteries and monsters beyond reason.

So, with that in mind, here are five of the creepiest mysteries that slithered out of Martin’s brain while he was writing. A warning now: we won’t be paying your therapist bill if you read on. 

Balerion and Princess Aerea’s adventure

Every scholar in Westeros knows that Balerion the Black Dread died of old age when he was well over 200 years old. What’s less well-known is that before his death, he was claimed by Princess Aerea Targaryen, a fiery young girl who’d grown tired of her sheltered life on Dragonstone. 

According to the book Fire and Blood, Aerea one day mounted Balerion, and the pair vanished. King Jaehaerys searched the Seven Kingdoms and beyond for his niece, but no one could find her or the great black dragon.

Then, a year after they vanished, the Black Dread was spotted over King’s Landing. Still, there was no time for celebration at the princess’s return as something was very wrong. Balerion, the most powerful living dragon, was covered in scars and bore a cavernous wound on his side as though some larger predator had tried to make a meal of him. 

Yet, as terrible as Balerion’s injuries were, they paled in comparison to the fate that had befallen poor Aerea. The Princess was rake thin and deathly ill. She burned with a fever that could not be broken, and Barth, the maester who tended to her, claimed that worm-like creatures were moving beneath her skin. Aerea cooked from the inside out until, finally, “unspeakable things” burst from her charred flesh, whispering dark secrets that Barth claimed he’d never forget. 

Exactly what had happened to Balerion and Aerea is unknown, but Barth believed the princess couldn’t control the dragon. As a result, when they’d left Dragonstone on that fateful night, Balerion had immediately returned home to the smoking ruins of Valyria. There, the pair may have been attacked by the insanities and foul creatures left behind after the calamity. Speaking of which…

The Doom of Valyria

Once upon a time, the Dragonlords used magic, dragons, and slavery to carve out the mightiest empire in the history of the Known World. Then, one day, it all came tumbling down when The Doom came to Valyria. 

What caused the cataclysm is unknown, but we do know that the volcanoes surrounding the city all erupted at once, choking the air and sending a tsunami of boiling lava into the streets. In a night, the Valyrian Freehold fell, and the once great city was consumed by the unleashed fury of liquid hot magma.

There are several theories for The Doom – including assassinated wizards, the Valyrians tapping into literal Hell, and bad luck – but the event itself, as horrible as it was, isn’t where the terror ends. What’s curious and creepy is that any attempts to visit Valyria have been met with disaster. 

Several expeditions have been launched to the city, but few have returned, and those that have, like poor Aerea, have been ruined by the experience. What lurks in the smoke and slat surrounding the once-great city? Is it wild dragons? Mad wizards or something even worse?

Only one person is confirmed to have visited, Euron Greyjoy (in the books), who’s currently plotting to become a dark god and destroy the world. So yeah, it’s not a place we’d recommend you visit. 

Black Stone and the Deep Ones

Not all mysteries in Westeros and the Known World revolve around the Dragonlords and their scaly friends. Some are far stranger and all the scarier for it. Take, for example, the oily Black Stone, which Martin references in his books. 

As the name suggests, this unusual ebony-colored rock feels oddly greasy to the touch and has been used to construct the city of Asshai. Anyone who’s read the books will know the city is famous for its dark magic and darker deeds, where the light of the sun is supposedly drank up by the sickly stones used in the city’s construction. 

Yet, as horrifying as Asshai supposedly is, it’s not the creepiest use of black stone. Both The Seastone Chair on the Iron Islands and the great Toad Stone on the Isle of Toads, one of the Basilisk Isles, are carved from oily black stone. 

While that may just be a coincidence, there’s more happening here than meets the eye. You see, the Ironborn have several legends about a race of aquatic fishmen known as the Deep Ones. 

Described as a “queer, misshapen race of half-men sired by creatures of the salt seas upon human women,” the Deep Ones are believed to be fish-human hybrids from long ago. Of course, that’s all superstition and nonsense, right? Well, then, why do the people living on the Isle of Toads have unpleasant, fishlike faces and webbed limbs? 

Could there really be a race of fishmen lurking in the seas around Westeros, or are they as real as grumkins and snacks, and this is just a playful reference to the Deep Ones from Lovecraft’s work? Well, people thought the White Walkers were just a story, and then they marched south, so who knows? 

Sothoryos and the City of Yeen

Sothoryos is the most southern continent in the Known World, and it sounds like a complete nightmare. Legends tell of dreadful creatures living in the dense, unexplored jungles, including tribes of cannibals, ghouls, and lizardmen.

It’s not just the people you have to be worried about, either. Lizards the size of lions, giant apes larger than giants, and venomous insects call the continent home, as do several deadly viruses and illnesses, including the infamous Greyscale. 

Yes, Sothoryos is a death trap, yet as harrowing as a trek through the jungles would be, it’s got nothing on the city of Yeen. This mysterious and ancient city was built millennia ago by an unknown civilization, and it has a foul reputation. 

Built of a strange oily stone (sounds familiar), the city has been abandoned for centuries, and any attempt to reclaim it has gone disastrously wrong. One notable attempt to settle the city by the Rhoynar saw the entire population of men, women, and children disappear overnight, as though spirited away by some dark presence.

Bizarrely, despite being uninhabited for so long, even the jungle hasn’t sought to reclaim the city, as though something foul has tainted the soil, preventing life from gaining purchase in the city. 

The Corpse City of Stygai

While Yeen is unlikely to feature on a list of the best vacation spots, it’s still better than a trip to Stygai. This haunted corpse city can be found in Essos and is believed to be full of demons and dragons. Even the sorcerors of Asshai give Stygai a wider berth for fear of what lurks in its empty streets and abandoned squares. 

Still, what makes Stygai so scary isn’t the spirits and monsters that are rumored to call the city home; it’s that it was abandoned in the first place. You see, the Known World is full of settlements like this, marvels of engineering that have been simply abandoned. Why did people leave their homes? What dreadful thing came and took their city from them? 

If you love the mysteries of Westeros as much as we do, then check out our guides for breaking down luminary figures like Blood and Cheese, Criston Cole, and Otto Hightower.

We’ve also got an article revealing everything you need to know about the new Thrones spin-off, Knight of the Seven Kingdoms. Finally, if you want to know more about the Tragaryen’s secrets, you have to read our piece all about Aegon the Conqueror.