In the purgatory of William Afton, the hell that was improved by Cassidy, William continued dying constantly, unable to do anything, as Cassidy did everything to make sure to enjoy a real show she could really enjoy, the show where William was not suffer but be killed endlessly by many different ways.
William passed decades, dealing with dying endlessly, but slowly, learnt patterns and loopholes he could use, but he needed time, something he had.
After a long time, he managed to memorize perfectly the loopholes and how to evade every animatronic. And after so long, he managed to break free from just sitting and letting himself get killed.
William ran, evading every animatronic, until entered a vent. He moved slowly through the vents, while some animatronics tried to trap him, but he noticed a little broken vent.
William broke it, and got out of the vents, falling down and noticing a little glitchy janitor supply room, where was also a Mimic endoskeleton turned off. The Mimic seemed very similar to what William saw long ago but forgot it existed. After few seconds, he heard the animatronics getting closer quickly through the vents, and so, William rushed himself and tried to turn the Mimic endoskeleton on.
When the Mimic turned on, its orange pupils glowed slowly, while everything slowly also started to burn down, and all the ambience had a orange glow lighting slowly more and more bright.
Cassidy hesitated, wondering why was everything on fire in a sudden, and why everything was orange lighted. She continued floating around, trying to search William.
The Mimic got up, and after a second of staring at each other, the Mimic barely killed William, but mainly, opening him up while being alive, to then get inside of his body to use it as a suit.
Mangle was the first one to get out of the vents, but the Mimic quickly grabbed her, and threw her against the shelves. The stuff on the shelves start falling down, as also one of the shelves too.
After a few seconds, Toy Chica appeared, and the Mimic grabbed her head, and easily threw her against the shelves too, and everything fell down. Then, the Mimic grabbed a pendrive that fell down from the shelves and was hidden, and which had a logo symbol of Glitchtrap.
After a short moment, Cassidy finally found him, and the entire map into darkness while glitching, but then quickly into Fazbear Frights location, and everything was still on fire and with the orange ambience light.
Cassidy hesitated, and from looking around, turned to look at William, but then she noticed, William's pupils were orange, and his expression was more than serious but a deep stare.
Both hesitated, but then, the Mimic slowly lifted his right hand, and from the pendrive he was holding on it, sudden purple glitchy lighting started appearing, and after a moment, the Mimic said it.
Mimic: "I ALWAYS COME BACK"
When the Mimic said it, William's body glitched, changing in instants between himself, Springtrap, Scraptrap, Burntrap, and Glitchtrap. But after a short moment, he glitched and vanished.
Cassidy hesitated, moving her arms from in front of her face, surprised by what just happened, but deeply annoyed by how he could have escaped, again.
Then, Cassidy also left, and appeared where she grabbed William's soul for second time. Everything was different, but she didn't care if was useless, and so, she moved, flying around in search for what she could use to make sure William was brought back to the hell she prepared, and from there, make sure he didn't escape again.
After a big search, Cassidy encountered Stephen Mega PizzaPlex. She was surprised, and after a short moment of appreciation of the location, she flied inside, but she got quickly disappointed by how it was the inside.
But after a search, she found the commemorative room to Billy, where was Billy the Rabbit still sitting and unmoved of his position against a wall. Cassidy hesitated, looking the walls, the pictures, while floated slowly towards Billy. After a short moment, she was in front of Billy, but then she looked up, noticing a Puppet mask on the wall a over Billy, but she then turned to look at Billy, and tried to wake him up, but there was no answer.
Cassidy tried again, she tried to wake him up, she needed what allowed her to take William's soul to purgatory, but Billy remained unmoved and not answering, and after some tries, she then notices Billy is empty. She moves closer, and notices nothing inside, just an endoskeleton, the springlock endoskeleton but different as was structured as the average endoskeleton but with reinforcements from the springlocks.
She hesitated, confirming to herself that Billy was gone, but that didn't stop her, as she went inside Billy. As she flied inside, Billy instantly reacted, shaking and convulsioning, as Cassidy started possessing it. After a short moment, Billy stopped moving, and his pupils started flashing and glowing red, until he was turned on.
Billy moved his head and right hand, looking at it, then to the other hand, and after observing itself, Billy slowly got up, and started walking towards the exit.
Meanwhile, in somewhere else, Stephen was in a workshop, where he finished building his own Mimic animatronic, not just an endoskeleton, but a complete animatronic that could change its body and limbs at will, mimic voices and behaviours, but also a container for gas as Goretrap had, and even a double syringe that extracts remnant and agony but splits it up into containers as one for remnant and another one for agony and is capable of not mixing both.
As Stephen waited, silence reigned, and boredom was clear, but he huffed and kept waiting, but nothing kept happening, until he injected a little more of Remnant. Is that when, the animatronic convulsed and had muscle spasms.
The animatronic's pupils flickered while opening, and it quickly moved up. Both stared at each other for a second. Stephen, glad for achieving it. The animatronic hesitant, but deep there, glad to see how loyal Stephen to help him get his immortality into more than just immortality, but real and undeniable immortality where he can't be drag out anywhere and is really an immortal being, even if that makes him something out of anything human.
Stephen: "Yes, you're back once again. Now, with a much better and improved animatronic. Why try to copy, when you can do something much better, right? And that's why I created this animatronic. I named it Revenant."
William hesitated, observing his new body, his new self. His fingers were sharp syringes, and on his left arm was a flamethrower. On his torso there were two big containers, the left one darker while the right one clearer and more lightful.
Stephen: "Much has happened while you were gone, Mr. Afton. Please, do follow me."
William turned to look at Stephen and noticed him bowing to him.