It liked it cold.
It made the boy aware of this very quickly, forcing him to tell his mother so when she prepared what both humans had referred to as a bath. If the boy had submerged himself in that hot water there was every chance It would have been forced from the boy, if the portion of itself within him could even escape in time.
It had only infested the boy, Will, for a few hours at that point. Not enough time to properly spread and assume control of him, it had made a poor decision when forcing the idea into Will's head that It did not like heat and to make his mother realise it.
It had not counted on the intelligence of these humans to piece together what it was and what it had done to the boy. But that had been Its one biggest mistake leading to its current agony; it had underestimated these people, both their intelligence and their determination to stop it and free the boy.
Every movement, every muscle was under Its control. It made the boy blink only to stop his vision and so therefore its vision from going blurry as the eyes dried from the cold air. Every breath was under Its control. The only reason the boy lived was so it could gain an understanding of this world and how best to infect it. Plus, it would need to learn how humans thought and acted. For It had to admit that whilst It was superior and would eventually consume the humans fresh unspoiled world they were more tenacious than It had first assumed.
First was the human who had destroyed the Demogorgon (as the boy's friends called it), the one that had also created the gate. This robbed It of its only minion capable of opening mini gates, small entrances into the human's world that would close after a time. Luckily the beast had gathered humans amongst other prey for It to incubate new Demogorgon's before its destruction. Even luckier SHE had not closed the gate, allowing continued access to that world. But SHE would be most dangerous, one that it still had not come up with a plan on how to deal with yet.
Then there were the humans guarding the gate itself. When It had continually sent vines and spores through the gate they had repelled it with fire, managing to actually hurt it. But unknown to the humans was the fact that it had been opening the gate further ever so slowly beneath the ground.
When the underground caverns were discovered they started to burn the vines, causing It to feel true pain for the first time. The small burns the human known as Hopper had caused to the vines earlier were, in comparison to the boys mind, like wasp stings: painful and annoying. As they burned the vines in earnest It writhed in agony, the pain shared amongst everything It was: the vines un yet burned, the Demogorgon's and the Boy.
This last one turned out to be what saved It from the burning pain and losing the tunnels to the humans. They realised that the boy was connected to It and that burning the vines would inflict pain on him, maybe even kill him. For reasons beyond its understanding the humans, who must have known that allowing the vines to spread would be their doom, valued the boy's life more than stopping It.
Seething from the pain these pathetic sentimental creatures had inflicted on It and realising it was Its connection to the boy that had lead the humans to the tunnels It focused on spreading through the boy's mind and controlling him. The boy had used It, now It would use him. Again, the humans were quick to realise the effect it was having on the boy, accidently wiping some of the boys memories in Its takeover, but they did not question when the boy said it knew how to defeat it.
It did not take any personal pleasure when It killed, in its world it had infected and consumed till it was the dominant life form of its world, it was merely surviving. But after the pain these humans had inflicted on it in the tunnels it took great satisfaction in butchering the soldiers sent where it had made the boy tell them would be its weakness. Then began the slaughter of the ones who had sent the soldiers, who continued to prod and poke and burn at the pieces of vines they had collected from the gate and tunnel.
Indeed, It had been so focused on hunting them down It had slipped its focus away from the boy and had allowed the boy to warn his mother and friends of its plan. It had quickly tried to reassume control but they put the boy to sleep, cutting It off from the boys vision and mind. Whilst frustrating It truly did not matter what they did with the boy; with its control of the gate it would not be long before it was able to spread the vines and its spores to allow its full being into this world.
It was surprised when they woke the boy, restrained in an unknown place, and if it was capable It would have laughed at their attempts to help the boy regain control and tell them how to defeat it. But as they spoke to him, the three that were family and friend, it felt resistance.
With each story the boy fought back, he wanted them to know he was still there, that he knew how to beat IT. Lips trembled, and It focused more and more on restraining the boys voice that it released control of the eyes and expression, even allowing the boy a few tremors in his hand since the boy was already restrained.
Then HE spoke, and It nearly lost. It did not understand what the boy, the friend, was talking about and did not care to investigate the boy's memories to find out; it was taking all Its effort to keep the boys voice from speaking the words that would ruin Its plans. Eyes watered, and sobs were building up within the boy. A few more seconds and the words would have come.
But the mother called the boys name and the distraction was all it took, for a second longer the boys' eyes watered, his lips trembled, and then It seized control of them both. The boy's hands still trembled but control of that was a small price to pay in exchange for keeping the boy quite.
For a while they left the boy alone in this room he, and therefore It, did not recognise.
He needed to get this boy away from these people and kill them if possible; they were becoming a threat he could no longer tolerate, especially if they were still in contact with that girl. He had checked the boy's memories for her almost as soon as It had infected him. She had apparently been missing shortly after killing the Demogorgon and had not been seen since. It had felt her presence in Its world, but she had disappeared as quickly as she came.
A pity. It had thought. With her body and abilities, It could have opened many gates and spread through this world by now. It let its attention wonder back to the vines, which continued to push at the walls of the gate, making it widen even further. Soon It would not even need fear the girl wherever she had chosen to hide herself.
Frustratingly the humans came back and tried once again to coerce information from the boy, but this time It was ready. It kept complete control of the boy's face and voice, fighting against him as each one told their stories. The tremor in the hand was still in the boy's control, perhaps he thought he could untie these restraints. If so he would focus on controlling the body and kill these fools, hopefully the boy would be in such despair that he would not try to take control again for a while.
Just as all of this was becoming beyond tedious a loud ringing noise caught both It and the boy's attention. The panic the boy felt at recognising the sound sent It rushing into the boy's memories, showing it to be the sound his home phone makes.
They were at the boy's home!
Quickly it sent this information to the Demogorgon's.
Realising their error, the humans put the boy back to sleep but not quick enough to stop what was coming for them. As the boy's body and mind drifted to sleep once again It focused its attention back to the Demogorgon's, pushing them as fast as they could to kill these pests. It looked forward to when next it looked through the boys eyes at the sign of his friends and family butchered. Perhaps he would no longer resist It, knowing it was his own memories that sealed their fate.
But now, as the boy awoke It felt a pain almost on par with the burning of the vines that were a part of It. The boy had been strapped to a bed, devices radiating heat had been placed around him, a fire lit near the bed creating even more heat. They knew Its weakness and seeked to purge it from the boy. Once again It was in an environment the boy did not recognise, meaning It could not send the Demogorgon's to rescue its host.
Despite the pain It knew whilst the mother, brother and another woman were present there was no sign of the one called Hopper, the friend or HER. SHE was the reason It had been so cautious, making the Demogorgon's hunt only wildlife instead of humans so as not to draw her attention, waiting until it was sure she was not around before possessing the boy. And yet on the very same night it finally made its move to enter and claim this world she appeared as if from air and killed one of the Demogorgon's it had sent with a flick of her wrist. It had recalled the others after that.
It had decided it would have to escalate its plans; It would come through the Gate tonight. The Demogorgon's would guard the gate whilst the vines stretched the gate wide enough for Its full essences, the "smoke monster" the boy had called It, to cross over into this world. It had tried, but the heavy material of the gate made it impossible for its vaporous body to push against and break through. The vines had been gathering strength and pushing against the walls of the gate whilst also creating the environment that Its true being could exist in. Without that or a host to hide in, its cloudy essence would start to dissipate. This it knew from an early attempt before the vines had taken root in the tunnels.
But it had not anticipated that the humans would discover its weakness and try to free the boy. If he were freed he would reveal how to kill the vines, the Demogorgon's and prevent It from entering this world all with one act. Worse was that they now had the one thing that could do it: the girl. If she closed the gate now not only would It lose all the ground and forces it had built up in that world, It would lose access to the world itself.
All that new food and hosts to infect and consume, denied him because of two children. It would not allow the boy to go free, it would endure the pain to keep the boy silent. It tried pleading through the boys mouth, hoping that once again the humans would put the boys safety above their need to stop it. But the hard and hateful expression on the face of the mother told It this time sentimentally would not stop the pain; she wanted the boy back and would see this through however long and painful it took.
It could not hold on for long, just as the brother started to protest what they were putting the boy through It felt itself being drawn from within the boy towards the surface of the skin. Desperately it manipulated the boys muscles, giving them just enough strength to break one of the bonds restraining his arms. Furiously It used that arm to try and break the restraint on the other arm, only to find the mother straddling the boy and trying to prevent that from happening.
This woman. It had underestimated her. It had underestimated them all but especially her. With all its hatred it took hold of the mother's neck and squeezed. The boy fought back furiously, the only thing preventing It from snapping her neck immediately was his resistance.
Fine, it thought, making the boy look into her eyes, lets watch her choke slowly instead then.
The brother leapt to his mother's aid, trying to pry the boys hand from his mother's throat, but the muscles It had stimulated in the boys arm were stronger than either of them.
Just as It saw the life start to fade from the mothers eyes a new intense and far hotter pain than the devices were giving off pierced the boys side. So intense was the heat that It had no choice but to release the mother.
As it recoiled from the pain It saw through one of its Demogorgon's that the human Hopper was at the entrance of the gate, alone and carrying a large gun. It may lose one or two Demogorgon's to that weapon, but It could not tolerate the human being this close to the gate. It prepared to have the pack guarding the gate swarm him in a tide of teeth and claws when suddenly—
BURNING AGONY!
The tunnels! Someone was in the tunnels and had started burning the vines! It had to be the girl! They had sent this human to the gate to distract It whilst the girl would destroy the vines making her way to the gate from below. It would have to deal with her and stop the fire from spreading all the way to the gate.
But the pain! It was too much. As it sent the Demogorgon's who shook with the agony all beings connected to It felt It made a final decision.
The humans at the gate were a far more pressing problem than keeping the boys mouth closed. Despite their attempts IT would succeed, It started moving its true essences towards the gates opening. It would cross over now and if It came across the girl in those tunnels it would make her Its new host, creating many more gates and spread throughout this world. It could not let keeping control of the boy distract it from these tasks.
The portion of It that was within Will erupted from his mouth like a swirling cloud of smoke, a fraction of its true form. Immediately it started to lose its essence, the atmosphere of this world breaking it down into nothingness, the heat accelerating the process. Feeling a cool draft from a gap in the door It gathered the last of itself from the boy and flew at and through it, destroying it in its haste.
The cold air outside was a relief from the heat but it was still losing mass as it rocketed up into the night sky. If it could make it to one of the tunnels and into the atmosphere the vines had created it would be safe and rejoin with its whole self. Currently this piece of the Mind Flayer, a name it was unaware it had been given by the humans, had gained a sense of sentience similar to the Demo-dogs (another name the humans had given to one of its minions). It could be given orders and would carry them out whilst Its focus was elsewhere.
As it flew through the night air towards the lake where the entrance to one of the tunnels was concealed It felt a sudden sharp jolt. The gate had started to close.
The girl! She had slipped past all Its defences and had started to close the gate!
Its true form was now at the entrance on its side of the world. It peered through as it ordered the Demo-dogs to return and kill the girl. Losing her as a host was unfortunate but if the gate was closed all would be lost. And It would not lose to these creatures, no matter how much it had underestimated them.
IT considered attempting to cross over now, to come through before the gate could be closed any further. But its mass was so big, it had no idea what would happen if even a small fraction of itself were trapped on either side. Which piece would Its consciousness be with; the one in the human's world, or the part that got left behind in Its world?
If too small a part was stuck in the human's world with the girl there was every chance it would be destroyed by her. It realized then that it actually feared her. It raged at the realization that a lowly creature had instilled fear in It. Before it had been cautious that she would kill its minions, it had never even considered that she could destroy IT. But now….
It would need Its full being to subdue and control her. Then when enough gates had been opened it would delight in killing her.
But as Its minions attacked and fell to Hoppers weapons it saw that indeed the gate was starting to close. The vines that had been pulling it wider started to stretch and rip from the force of the closing gate. The thread like material that covered the gaps between the two worlds started to reconnect and repair itself, making the gaps Its essence could travel through become smaller and smaller. The sight of this pushed It to make its decision.
It sent a tendril of its smoky essences through the gate and sent it straight towards the Girl. There may be a struggle to control her but whilst they fought for control her attention would be away from the gate. And it still had many Demo-dogs to throw at her and Hopper, sooner or later It would win.
But just as she was about to be within Its reach the girl roared in a rage, blood pouring from her eyes and ears. She levitated from the platform they had used to reach the gate.
Suddenly It could not reach any further, like an invisible wall had come up between her and It. Then came pain, pain that dwarfed the flames this world had exposed it too. Every part of itself that connected with this wall was shredded into nothingness. Then the wall started to push ever so slightly forward, pushing it back towards the gate, which it realised had not stopped closing but instead had accelerated. It was very nearly closed.
The Mind Flayer roared at the girl from its side of the gate.
It had lost.
As It withdrew its smoky tendril just in time it felt its connection to the Demo-dogs and the vines cut off. It did not see the dogs fall or the vines stop their twitching but new that without Its connection they would move no more. The humans had beaten it.
And it seethed with that thought.
But unbeknownst even to the Mind Flayer a small piece of it had survived. But not for long if it could not find a host.
It had finally flown over the lake by the time the gate had finished closing. And what pain that was. It did not hear its master's calls and just as was the case of its "body" its consciousness was starting to fade. It plummeted towards the ground, landing in a little clearing just by the waters edge. It drew its essence to itself, a mass of swirling smoke no bigger than a kitten now.
Its "mind" knew only three things, find a host, blend in, await orders. But even these thoughts were becoming hazy.
Suddenly, movement.
A creature, tinny, had come to investigate the commotion. If It had still been connected to the boy it would have identified it as a rat. It came closer, sniffing cautiously at this strange phenomenon that had landed near its nest.
Losing more and more of itself by the second the piece of the mind flayer invaded the body of the little creature who had come to inspect it. Its mind would have been easy to dominate, but without orders from its master It became little more than a passenger to the rat's needs.
As the rat returned to its nest in a little tunnel under a tree root It became aware of the sound of many tiny squeaks, then saw that this rat was the mother of a litter of seven. All of them were screeching for their mothers milk. Getting into position she allowed her mischief of rats to suckle on her.
As each rat drank its mothers milk a tiny portion of the mind flayer spread to the newborns, infecting them with a portion of itself. It did this unknowingly, its consciousness barely present in each new host it gained. But It would survive, infecting every new born rat that came from the offspring of each of these baby rats, and it would wait for its masters return. Until then it would be nothing more than a parasitic passenger, sleeping and waiting for a chance to serve again in this dark cold tunnel.
It liked it cold.