Disclaimer: I don't own them.
A/N: I wrote this when I was writing 'Myself and I' which is up on my author page. So if something sounds similar you know why ;) This is also a warning since it involves character death.
At The End of Hope
After the first terrifying week of having Lucifer visit him in his dreams and calling Dean who insisted that they stay apart, it was becoming too much for Sam. So much so that he almost broke down and released Sammy from the stronghold section of their shared psyche.
When Sam first arrived in town, he knew that in order to survive by himself and be strong, he would have to manhandle the Sammy part of his psyche into the deepest corner that existed. Sammy still wanted his big brother, Dean, to save him, to be there for him and Sam knew that Dean just couldn't.
So he set out to bury Sammy so deep that he just about forgot that once he was another carefree person, was once a hunter, and most importantly was once a little brother to one of the awesome big brothers who ever existed. It helped when he had burnt all his fake IDs and credit cards so that there wouldn't be a reminder of what he had lost.
Lucifer still came and visited Sam in his dreams, taunting him with the likes of Jessica, his parents, and of course Dean. At first Lucifer came in Sam's dreams as he slept at night, but when Sam didn't say 'YES', Lucifer started haunting Sam in his waking hours by visiting him in hallucinating daydreams.
Lucifer always ended his dream visits asking Sam if he wanted to say 'YES'. Sam always replied, 'NO'.
As the days turned into months, Sam went through life just existing. He worked diligently and stuck up a causal friendship with Lindsey, who so unbelievably, stood by him when hunters ambush both of them and forced him to drink demon blood.
There were times where Sam called Dean, who never answered. On the rare occasions in which Sam called Bobby, he would beg Sam in his gruff voice, to just come back to them. Sam would always refuse.
Other times, Castiel would call Sam and only he had the courage to plead with Sam not to give up. Give up on what, Sam never knew. As far as he knew, he had nothing to live for. That's not true, a whisper came from the deepest pit of Sam's psyche. You still have Dean i Sammy so achingly whispered in his longing for Dean.
In the end, Sam's determination not to say 'YES' was for all nothing. Eventually, Lucifer's relentless pursuit of him broke down Sam's defenses, taunting him with various stories about Dean and the reminder of what was left of Sam's friends, of Bobby and Castiel.
One moment he was still Sam and the next he was a walking nightmare, wrecking havoc on humanity with glee.
Lucifer used to whisper into Sam's ear that he should just let him in fully. Isn't it enough that he has my body, Sam mused to himself. When Lucifer had first taken over, the snippet of Sammy was still locked deep in a cherished cavern of Sam's self. Sammy was the one part that Dean really adored and loved unconditionally and Sam was determined that Lucifer wouldn't get a hold of it. It was the last connection he had to Dean.
Sammy was Sam's version of keeping hope alive. He hoped that if he kept that part of himself away from Lucifer, then eventually he'd be saved.
Throughout five years of having Lucifer wear him as a prom dress, Sam kept Sammy and hope close to him, trying to keep something good alive.
But as Lucifer's white dress shoe broke Dean's neck, Sam finally let his strong hold on Sammy loose and let him try and brush alongside Lucifer's more powerful psyche. Sam didn't know what Sammy would do in a rage at seeing his beloved big brother dead, all Sam knew was that he was standing at the brink of nothing, at the end of hope.