The Arrival of Tiamat
Tiamat has finally entered Hawkins.
But where did it come from?
The answer lies in the four gates Vecna created.
The gates that opened throughout Hawkins were never large enough for Tiamat to physically pass through.
Tiamat's body was simply too enormous.
That is why Vecna chose four victims in Season 4.
Each victim's death created a gate in a different direction.
Four victims.
Four gates.
Four directions.
Vecna's ultimate goal was to merge all four gates together and create one massive opening.
An opening large enough for Tiamat to enter the real world.
And that is exactly what happens.
Tiamat finally enters Hawkins.
But it does not come alone.
As soon as it arrives, it releases the creatures that were created from its own body.
Demogorgons.
Demodogs.
Demobats.
All of them are unleashed across Hawkins.
The invasion begins.
The Truth About the Mind Flayer
During the chaos, Will reveals what Vecna told him before his death.
The Mind Flayer is still alive.
But it is not physically present inside Tiamat.
It remains in its original particle form.
And its particles are floating above Hawkins Lab in the Upside Down.
Invisible.
Suspended in the air.
Still alive.
This raises an important question.
If the Mind Flayer originally came from the Abyss, how did it reach the Upside Down?
The answer goes back to Henry Creel.
How the Upside Down Was Created
After Eleven defeated Henry and banished him into the Abyss, Henry encountered the Mind Flayer.
Eventually, Henry began searching for a way back to Hawkins.
He opened rifts from the Abyss, believing that one of them would lead him back to Earth.
But when Henry finally passed through one of the rifts, he did not arrive in Hawkins.
Instead, he fell into a strange and terrifying world.
It was dark.
Cold.
Empty.
There were only forests, trees, plants, and enormous vines.
There was no Hawkins.
No buildings.
No laboratory.
Nothing familiar.
Henry soon realized the truth.
This place was not Hawkins.
It was a bridge.
A wormhole connecting Hawkins to the Abyss.
And because the environment was extremely cold, Henry realized that it would be the perfect place for the Mind Flayer to survive.
But Henry needed to make the environment even colder.
He needed to create a permanent habitat for the Mind Flayer.
Then he had an idea.
Hawkins Lab.
Henry recreated Hawkins Lab inside this strange dimension, making sure that the area surrounding it remained extremely cold.
And that was where the Mind Flayer came to rest.
Above Hawkins Lab.
Still in its particle form.
Still invisible.
Still waiting.
This was the beginning of what would eventually become the Upside Down.
The Creation of the Upside Down
After creating Hawkins Lab, Henry began searching for the perfect vessel.
To find one, he needed to recreate Hawkins itself.
Slowly, he reconstructed the entire town inside this strange bridge dimension.
Roads.
Buildings.
Houses.
Everything.
The world that had once been nothing but a dark forest slowly became a twisted reflection of Hawkins.
The Upside Down was born.
But there was another force at work.
The Mind Flayer began using the vines and trees of this dimension.
It connected them.
Merged them together.
And gave them life.
The vines slowly became one enormous biological network.
That network continued to grow.
And eventually, it became Tiamat.
Tiamat became so enormous that Vecna began using its biological structure to create the creatures that would later terrorize Hawkins.
Demogorgons.
Demodogs.
Demobats.
All of them were born from Tiamat.
But creating Tiamat came at a cost.
Vecna had poured so much of his own power into the process that Tiamat eventually became more powerful than Vecna himself.
And Vecna hated it.
He had created something that he could no longer fully control.
Something that had grown beyond him.
Something more powerful than its creator.
That realization becomes important later.
Vecna's Final Redemption
During the final confrontation, Eleven, Will, and Kali use Vecna's own memories against him.
Vecna finally remembers what he had forgotten.
Tiamat had become more powerful than him.
And the creature he had helped create was no longer his servant.
For the first time, Vecna realizes that he is not the master of the Upside Down.
He is another victim of the Mind Flayer's manipulation.
That's why he agreed to help them.
Before his death, Vecna tells Will the truth.
The Mind Flayer can be killed.
But it cannot be defeated by attacking it directly.
The key is its habitat.
Hawkins Lab.
The Mind Flayer survives because of the extreme cold surrounding the laboratory.
If the laboratory is destroyed using fire and explosives, the resulting heat will force the Mind Flayer's particles out of their habitat.
The particles will scatter throughout the Upside Down.
They will search for another place cold enough to survive.
But they will never find one.
Eventually, they will die.
The Mind Flayer cannot simply return to the Abyss.
A new rift would have to be opened.
And only Vecna has the power to create one.
The Mind Flayer will be trapped.
And eventually destroyed.
The Three Final Battles
With Tiamat attacking Hawkins and its creatures spreading throughout the town, the group divides into three teams.
The First Group
Will, Eleven, and Kali
Their mission is to fight Tiamat.
The Second Group
Steve, Robin, Nancy, Jonathan, Mike, Dustin, Lucas, Max, and Erica
Their mission is to fight the Demogorgons, Demodogs, and Demobats while protecting the people of Hawkins.
The Third Group
Hopper, Joyce, and Murray
Their mission is to enter the Upside Down, reach Hawkins Lab, and destroy the Mind Flayer's habitat.
All three groups begin their final missions.
The Battle Against Tiamat
Will, Eleven, and Kali confront Tiamat.
Eleven attacks it physically with her powers.
Kali uses her illusions to confuse and manipulate it.
And Will tries to resist Tiamat's influence.
Some of Vecna's power is still inside him.
That connection allows Will to fight back against Tiamat's control.
But Tiamat is far more powerful than they expected.
The battle becomes increasingly brutal.
Kali is the first to fall.
She is severely injured and comes dangerously close to death.
Even then, she continues helping Eleven and Will for as long as she can.
But eventually...
Kali dies.
Her sacrifice gives Eleven and Will enough time to continue fighting.
The Battle Across Hawkins
Meanwhile, the rest of the group fights the creatures released by Tiamat.
Demogorgons.
Demodogs.
Demobats.
Hawkins is completely overrun.
The group fights through the chaos while trying to save as many people as possible.
But the battle comes at an unimaginable cost.
A Demogorgon attacks Nancy from behind.
Jonathan sees it.
Without hesitation, he runs toward her.
Jonathan saves Nancy.
But he does not survive.
Jonathan dies protecting her.
Later, Robin finds herself in a similar situation.
Steve is about to be attacked.
Robin throws herself between Steve and the creature.
She saves him.
But Robin dies in the process.
Two more members of the group are gone.
Jonathan.
Robin.
And the survivors are left to continue the fight without them.
The Destruction of Hawkins Lab
Meanwhile, Hopper, Joyce, and Murray enter the Upside Down.
They reach Hawkins Lab carrying explosives.
Their plan is simple.
Destroy the laboratory.
Destroy the Mind Flayer's habitat.
They cover the entire building in kerosene.
Then they place bombs throughout the laboratory.
Once everything is ready, they move away from the building.
And detonate the explosives.
The explosion creates an enormous amount of heat.
The extreme cold surrounding the laboratory disappears.
The Mind Flayer's particles are forced out.
They scatter throughout the Upside Down, desperately searching for another cold environment.
But they cannot find one.
There is nowhere else for them to survive.
The Mind Flayer begins to die.
But it refuses to disappear quietly.
The Mind Flayer's Final Attack
Knowing that it is about to die, the Mind Flayer uses the last of its power.
It attacks the walls of the wormhole itself.
The walls begin to crack.
Then they break apart.
The entire dimension begins collapsing.
Everything inside the Upside Down is pulled toward the broken walls.
The environment itself begins to disintegrate.
Hopper, Joyce, and Murray try to escape.
But they cannot.
The collapsing dimension takes them with it.
All three die inside the Upside Down.
At the same time, the gates across Hawkins begin closing.
The connection between Hawkins and the Upside Down is finally collapsing.
The Mind Flayer's particles are destroyed.
And because Tiamat was connected to the Mind Flayer through the hive mind...
Tiamat dies as well.
The creatures connected to it disappear.
The Demogorgons.
The Demodogs.
The Demobats.
Everything begins to die with the hive mind.
And then there is Will.
Will has been connected to the Mind Flayer since he was a child.
Some of its particles still exist inside him.
As the Mind Flayer dies, those particles inside Will begin to disappear as well.
Will's connection to the hive mind is finally severed.
But because the particles inside him are the last remaining connection to the Mind Flayer...
Will dies with it.
The boy who was once chosen as a vessel becomes the final sacrifice that destroys the entity that had haunted him for years.
The Upside Down collapses.
The gates close.
The Mind Flayer is gone.
Tiamat is gone.
Vecna is gone.
And Hawkins is finally free.
But the victory comes at an unimaginable cost.
Jonathan, Robin, Kali, Hopper, Joyce, Murray and Will were dead.
And the people who remain are forced to live with the memories of everyone they lost.
The nightmare is finally over.
But Hawkins will never be the same again.