This is an old Finish the Story ending, that I did not, in fact, finish. But then I refound it and now I have! The beginning is an atmospheric and creepy piece called Horror Vacui by 
Image by Eak K.
f3nix's beginning
The moonlight descended on the east side of the Wagner Tower like an ancestral bone dust. The ectoplasm of a vague awareness crossed a tenant’s mind seeking for oblivion: finally, the dull blows coming from God knows what remote corner of the old building had decided to quit and he would have slept. However, between the seventy-fifth and seventy-fourth floor, a particularly fine ear could have still seized an intermittent, stifled counterpoint of voices.
“I feel that this unusual condition is helping us bring out some interesting perspectives, Mendo.” In breaking the silence, the psychotherapist’s voice had soon lost its initial momentum.
“...”
“I want you to know that this time won’t be billed, go ahead if you feel like it.” She tried to assume a playful expression. Hidden underneath her short suit jacket, Dr. Wallace’s fingers were nervously playing with a fluorescent orange rubber bracelet.
“No-one is ever suspended, not even now with seventy-four floors of nothing underfoot...”
“Well, this is certainly a positive observation...”
“Shut up, you don’t not know a shit.” An almost calm remark, pronounced with a firmness that hit Dr. Wallace like a bucket of frozen water.
“Have you ever thought, doctor,” Mendo continued, sharply spelling out his last word, “that the fear of emptiness, the horror vacui as they defined it in the Middle Ages, is nothing but the unconscious and desperate attempt to look away from the ultimate truth?”
Since the elevator had blocked its descent, the patient had confined himself to a corner on the opposite side of the entrance. His left leg was now dancing grotesquely, animated like it had a life of its own and in contrast with the cadaveric stiffness of his other body parts.
“I never thought of that.” Dr. Wallace wisely responded in brief, observing for the umpteenth time the assistance number carved on the elevator control panel.
“Mmmm...” A growing moan on the other side of the narrow cabin.
The doctor instinctively thought of her daughter that night, when the wind had hit the fixtures of the old house in the mountains so intensely that it produced an endless banshee howl. The little girl had made a sound of compressed horror, just like that.
If only she had known, she would have never asked Mr. Anatoliy “Mendoza” Volkov, an extraordinarily subtle personality, to follow her downstairs after that emergency therapy session in her office. On the other hand, he was one of her first and most challenging patients. Furthermore, he used to pay awesomely.
“Because the void swarms.” Now his eyes were on the doctor, sunken out and bugging out at the same time.
“Soon they’ll free us, do you think you’ll keep writing that song you were talking about?” Dr. Wallace ventured. She realized that the silk shirt was soaking with her acrid sweat.
“It’s the Yellow King’s dominion, he comes from the void, it’s him who made me do those things. I did not want to.” His whine ripped open in a sinister vocal of terror.
“Mendo ..” She did not know what to add. Now the doctor’s hand, behind her sweating back, was pressing the assistance button convulsively.
His wide open eyes. They had stopped staring at her and now they were pointing up, right behind her shoulders.
“Mendo, what’s up?”
“The Yellow King. He’s here.”
My ending
She didn’t turn. She didn’t have to. There was nothing outward to warn her like the intake of breath or the rustle of clothing. He had no need for either, but all the same she felt his presence and was relieved.
When she spoke, she could hear him repeating her words a syllable or two behind, his voice a dull, bass hissing stripped of all inflection.
“Is he?” she asked. “The very one responsible for your crimes?”
“…crimesss.”
Mendo’s mouth opened and closed reflexively, gasping for air and understanding at the same time. Years of schooling her face into an expression of clinical detachment kept Dr. Wallace from showing any amusement or smug triumph. Although his insults had stung, she hadn’t done this as a cheap parlor trick to prove a point. Real fear had made her call out to her lover and it was pure luck they had stopped between floors, suspended in a liminal space which made it easier for him to pierce the veil and come to her aid.
She noticed Mendo’s left leg had stilled. Perhaps it was an affectation, like the compelling lies which had once half-convinced her he might be an Initiate as well. If she’d had any doubts left, his reaction now would have cleared them.
Contempt flared up for Mendo and those like him, people who danced at the edge of the abyss but shook in fear should the ground wobble beneath them. The Yellow King’s touch traced down to the small of her back and circled forward. She knew he was enjoying this, as he always enjoyed the fire of human emotion. His tendrils tightened over her hip and fanned up into her jacket. She had to stop herself from pressing back against him.
A loud thunk and then several metallic squeaks came from outside of the car. Mendo’s deliverance was near but there was still time to get in one final taunt.
“Have you nothing to say to your alleged master?”
“…masss-ter.”
A slim, dark coil flicked out and caressed the side of Mendo’s left leg, setting it into jerky motion again. He let out a high-pitched whimper and extended shaking hands with palms outward, an ineffectual warding off.
But tonight he carried the protection extended to madmen and fools. The inner door rolled slowly sideways and the tendril shot back like a snapped cable. There was no physical phenomenon to accompany the Yellow King’s departure but Dr. Wallace staggered slightly at the sudden absence.
The night security guard’s smooth face peered in at them and was arrested by Mendo’s spastic movements. He frowned. The doctor had plenty of time to adjust her suit coat back to normal before his attention turned to her.
“Sorry it took so long to get to you, Doctor,” he said, eyes still on Mendo.
She resumed her appointed role swiftly, casting a pitying look at her patient.
“Perhaps we’ll get Mr. Volkov out first. I think he’s found our…interlude a bit upsetting.”