‘Stranger Things’: A Guide to The Upside Down’s Monsters

You can’t have Stranger Things without The Upside Down and all of the monsters it houses. From Demogorgons to Vecna (Jamie Campbell Bower), learn about the creepy creatures that go bump in the alternate dimension in this helpful guide.

Demogorgons

There’s nothing like the O.G. ogre! In the Stranger Things universe, the Demogorgon emerged as Season 1’s menacing monster, terrorizing Hawkins, Indiana. The big bad, standing over 8 feet tall, with a humanoid body and giant flower petal-shaped mouth, memorably killed Nancy’s (Natalia Dyer) bestie Barb (Shannon Purser).

The seemingly sole Demogorgon was obliterated by Eleven (Millie Bobby Brown) using her psycho-kinetic powers. The creature later popped up throughout the series. We learned they begin life as sluglike larva, such as the one Will (Noah Schnapp) throws up into the sink, and later become pollywogs, like the critter Dustin (Gaten Matarazzo) finds and names Dart that eventually grows into a Demodog.

Most recently, we saw Demogorgons fighting prisoners at a Russian gulag where Jim Hopper (David Harbour) faced down the interdimensional killers. THREAT LEVEL: 4 out of 5

The Mind Flayer

After Will’s return from the Upside Down, things weren’t quite right. It’s clear he still had a connection to that alternate dimension, and that became even stronger when the Mind Flayer took over his brain and body in Season 2. The black cloud, extended with giant tornado tendrils, loomed large over an already traumatized Will as his mind shifted between his real life in Hawkins and a coexisting connection to the underworld.

From there, Will progressively lost control of himself until his friends and family caught on. Despite the creature overturning Will’s consciousness, it wasn’t unbeatable; heaters and a hot poker were able to exorcise the monster from the boy. Still, its ability to touch its host from another dimension made it a truly terrifying Stranger Things creature that barely showed its cards in Season 2, upping the ante in a more physical way in Season 3. THREAT LEVEL: 3 out of 5

The Flayed (controlled by Mind Flayer)

Technically, Will was the first Flayed, until the Mind Flayer was pushed from his mind and body. But that didn’t stop the baddie from attempting to attach itself to other vulnerable humans around Hawkins, kicking off Season 3’s monster plot. When a rift to the Upside Down was opened beneath Starcourt Mall, it created a link for the Mind Flayer to reconnect with the real world. The Mind Flayer infected rats at Brimborn Steel Works, later migrating into select humans around Hawkins, including Max’s stepbrother Billy Hargrove (Dacre Montgomery). The Flayed — aka the pack of possessed humans — became a physical embodiment of the Mind Flayer outside the Upside Down.

Billy’s possession was the most extreme, and despite various attempts to break the tie of the Mind Flayer, it wasn’t until the monster was defeated in the real world that the bind was disintegrated in Billy’s tragic final moments. THREAT LEVEL: 2 out of 5

Spider Monster

The spider monster is the organic and physical embodiment of the Mind Flayer, formed by the disintegrated bodies of the Flayed. Resembling the black cloud shape that haunted Will’s mind in Season 2, this creature terrorized the town of Hawkins and its crown jewel — the Starcourt Mall — in the back half of Season 3.

Its large and imposing stature left characters scrambling to find a way to defeat it, including Eleven, who faced her biggest threat to date as the Monster attacked her and her friends in Hopper’s cabin. During that assault, matter was left behind under Eleven’s skin, allowing the Spider Monster to track the group to Starcourt, where the epic final battle of the season ensued.However, once the gate to the Upside Down was closed beneath the Starcourt Mall, the fleshy, horrific creature became lifeless. Still, the sheer size of the Spider Monster alone would make the bravest Stranger Things warrior tremble with undeniable, understandable fear. THREAT LEVEL: 4 out of 5

Vines

The vines have been synonymous with the Upside Down since the beginning, and their influence expanded as the series unfolded. It’s been revealed to viewers that the Mind Flayer has always been in charge of everything they do. Serving as a nervous system of sorts, the twirling, tangling root and shrublike beings had a much more nefarious purpose than was originally observed in the series, making the Vines a threat worthy of monstrous recognition.

Whether they were tethering Will physically to the Upside Down in Season 1, constraining Hopper in Season 2, or acting like an alarm system for Vecna as Nancy, Steve (Joe Keery), and more invade the Creel house from the Upside Down in Season 4, there is more than meets the eye when it comes to these creatures. The bottom line? Don’t get too close, as you never know what might try to grab you. THREAT LEVEL: 2 out of 5

Demobats

A species related to the Demogorgons, the Demobats were introduced in Season 4 just in time for a sense of satanic panic to hit Hawkins. After the town experienced a series of murders, suspicions were raised regarding Hellfire Club leader Eddie Munson (Joseph Quinn), mainly because of his penchant for Dungeons & Dragons. While the teen had nothing to do with the killings, he had the power to keep the Demobats from attacking several friends as they infiltrated the Upside Down. He entranced the creatures with tunes from his guitar until they attacked and killed him.

Similar in look to the real-world winged mammals, the Demobats are used as spies for Vecna in the Upside Down. These bats have plenty of bite as they fly around the Creel house in this scary alternate dimension. And beyond Eddie’s death, they also took a stab at Steve, the group’s babysitter, which cannot be forgiven. THREAT LEVEL: 3 out of 5

Vecna

Vecna is the man behind the curtain, the evil Oz to Stranger Things‘ Emerald City, as he lords over the Upside Down. Banished to this underworld by a young Eleven back when he was Henry Creel, Vecna’s human appearance quickly altered under the harsh conditions, blending him into his surroundings while also allowing him to harness his extreme powers to pull the strings of all the creatures residing alongside him in that dimension.

Possessing most of the powers from the aforementioned creatures, Vecna can haunt the minds of the vulnerable. He went on a murder spree, breaking his victims’ bones, imploding their eyes, and delivering extremely gruesome endings. While those at the heart of the show seemed to find a way to combat the attack using music (thank goodness for Kate Bush!), their attempts to take Vecna down for good were futile, setting the stage for Season 5’s final showdown. THREAT LEVEL: 5 out of 5

For an extended celebration of Stranger Things, from a Season 5 preview to must-see photos and more, pick up a copy of TV Guide Magazine’s Stranger Things: The Final Chapter special issue, available for pre-order online now and on newsstands now.

Stranger Things, Season 5 Volume 1, Premiere, November 26, 2025, Netflix

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Stranger Things, Season 5 Finale, Premiere, December 31, 2025, Netflix and Select Theaters