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The man stood at her door, dark and imposing. He wasn't a large man by any standards, he wasn't small, of course, but he had an air about him that would send shivers down even the most foolhardy of the men in this world.
Yet she was no man.
The man moved, from his statuesque stillness, to knock at her door, only to watch it open before his knuckles reached its ebony surface. "Come in," was all she said, all she needed to say. He obeyed silently.
She had been expecting him.

You see, the Devil only moves to make deals when he has something to gain, as is his nature: opportunistic and self serving, idle and passive to the very moment he is guaranteed victory, leaving only bait to draw them in. As such, the Devil is a hard man to trick.
But Miss Elizabeth did it.
I'm getting ahead of myself though.
The Devil had dressed sharply for the occasion, wearing the darkest and sleekest of his black suits, he looked fit to go to a Royal Ball.
So did Miss Elizabeth.

It happened in a small, dusty town in South-West Tennessee, a few years after the Civil War, its name is unimportant and all else that need be known is that it was like all others of its kind: superstitious and racist. And as such there were many rumors pertaining to Miss Elizabeth, as there were of all single women of the time, most of which were horribly off base, but some struck quite true. The most off putting of them all, though, was the one she had started herself: that she'd have killed that son of a b***h if he came back from that War alive.
Miss Elizabeth had always been single, but for a time there had been a suitor. Don't quite know why he was so obsessed with her, might have had something to do with her striking beauty though, as she would barely associate with him in public. Yet still he would talk bounds of her beauty and his love for her in public and she would gossip of his devilish good looks and his money among her lady-friends. But in private Miss Elizabeth cursed him for his gambling and drinking and for his philandering ideals. Though in the end he had gone off and died in the Civil War, leaving everything he owned to her, thus that is neither here nor there.

The man sat down on the sofa, his black suit clashing horribly with its delicate floral pattern. The silence fell back over them and resumed its deafening rampage. The tension in the room wasn't simply palpable, it was a veritable monster, skulking in the corner, silently awaiting the time when it would lash out at thee first to speak. Yet to look at the two in the room, both cool as ice and emotionless, you'd never know, you might even suspect that the tension was something imagined by the silence, you'd be wrong.
The man sighed and leaned forward, intending to speak, but she silenced him and spoke instead. "I know that you're here for your end, do not fret, you will get it soon," she said and the man nodded in resigned acknowledgment.
She called the shots here.

Maybe it was the personal nature of this deal that caused the devil to risk more that time, maybe he had become drunk on his success... Perhaps he really had fallen for Miss Elizabeth. But whatever the case, whatever the circumstance, one careless truth, issued from the Devil's very lips, had allowed Miss Elizabeth to take what was once simply a deal with the Devil and turn it into something far more sinister.
The Devil's plan had started as a simple desire, the want for contact, and over the years it had built up and coalesced as the need to wed. And so the Devil waited for the woman that he would make his.

"Where is she?" the man asked in a voice raspy and strained, as though it had been hiding in his sadness for many months, yet you could still hear the velvet that it was once made of, if you listened well enough. The man watched her leave him to sit in the momentary emptiness that filled the room in her absence.
She came back with a knife to the young girl’s throat.

It would be that Miss Elizabeth wasn't the first woman that met the Devil's standards. Eight years prior though, the woman who would be Queen of Damnation at his side was taken from him in the act of bearing him a daughter. Contrary to what you'd expect, the Devil was a good father, the kind of father that would brag about his daughter to the woman he attempted to court.
Thus unfolded his mistake.

"Now give me what you promised, and I will let her go, Lucifer," Miss Elizabeth belted out.
"Once you give my daughter back," the Devil responded, knowing that the first to give in would lose everything.
"Go through with it or I'll kill her now," the Devil had seen that ultimatum coming and knew what it meant. He sighed and started the ritual, finally accepting what he knew all along: he'd sacrifice everything to give his daughter a snowball's chance in hell at living her life. As the ritual drew to a close the Devil found himself darkly chuckling at his own desperate hope that hell really had frozen over that day.
The man who once was the Devil watched his daughter fall to the floor, blood pouring from the wound on her neck. The grief that caused him registered distantly, he saw that coming, he would have done the same. Miss Elizabeth's smile, a smile so full of gleeful malice that it chilled him to the bones even as he was consumed by the dark hellfire he once controlled, was the last thing he saw.

Miss Elizabeth disappeared that day and the entire town knew, although no one said it aloud and fewer had proof, that: The Devil is a Southern Belle.

It's a very short story, but it could be more I suppose, where are the run-on sentences? I'll see if I can correct them, although it's very likely that I couldn't fix them.

Aw man, I don't think I'm going to change that one, it was one of my favorite sentences in the entire thing. That and the colon saves it from being a true run on, mostly.

The colon relates two different ideas together, so those technically are already two sentences, the colon just relates one to the other. (It also refers to the start of a special kind of list)(Also, the way you just used that colon was almost exactly the same way I used one in my sentence.)