From the Void, the Master

She had stopped caring what lay beyond the window at one point or another in the night, but when, finally, the creature released her back down onto her bed, its tentacles retracting, sliding back into its humanoid form without a care for the available storage space, she could see that the sun was just beginning to rise in the distance, long shadows beginning to recede even now. They had been at this all night long.

... At least the creature was breathing heavily too.

Personally, she could barely raise her head to look at it, her muscles turned to jelly after her intensive workout. Sweat ran in rivulets down skin flushed with exertion, bruises and sucker-marks dotting her usually milky complexion, perhaps the only evidence after this night of what had happened to her. Her pussy dripped freely, her own arousal mixing with the alien compound that had transformed her body into that needy live wire of passion, that had kept her going, wanting more for hours at a time. She wished, fervently, that she could bottle the stuff.

One tentacle remained wrapped around her neck, not tightly, not enough to cut off her breathing, but enough for her to know that it wouldn't be dislodged by her mere resistance. Not that she would want to resist it, anyway; she nuzzled into it, breathed in the scent of starlight and, oddly grateful for the night they had shared, kissed it. Regarding the entity with tired eyes, she could have sworn she saw it react to that, though in truth it had been oddly still for quite a while now.

It raised a single hand, flexed, and behind it the same window to another world that it had entered through in her dreams opened up behind it, fading into existence like a cheap special effect. She supposed that reality didn't owe her flashiness, but nevertheless, it was disappointing to see.

The creature turned, looked into the new, uncharted realm beyond the doorway, silently.

And then it looked back at her, purpose glimmering in its eyes.

It waited, still and tranquil, for her to realize; the tentacle around her neck was not an embrace, not some fond farewell. Eldritch horrors were not known to be sentimental like that. No, it was a collar, a collar and a leash, to lead her wherever the creature wanted her to go. Perhaps as a mate, perhaps a pet... all was in doubt, expect the promise of more to come, those same desperate heights of pleasure, untethered from the limitations of reality as she knew it.

She took the time to look, narrowing her eyes as she gazed past the creature into its doorway. If she looked past the stars she could see them, stamped midnight black against the void: tentacles, filling her vision, in every conceivable size, writhing and wrapping together, the totality of whatever realm lay beyond the window...

... All of them, belonging to the being that stood in her bedroom, waiting for her to speak. She knew this, in the marrow of her bones, without ever having to be told.

Words weren't necessary. It was doubtful that her partner would have even understood them if she said them. Loose-limbed and shaking, she slid off of her bed onto the floor, her legs unstable beneath her. Chirruping again, the entity began to walk, and she allowed herself to be led by her new collar toward the endless depths of its true form.

Tentacles reached out to meet her, embracing her across realities, stroking her hips, the inside of her thighs, even between her legs as the creature made its final step across the threshold just a moment before she did. Heart racing, she surrendered herself to the tentacles, arms wide as they held her, bore her through into a weird new world.

The portal began to seal up behind her, leaving no trace that it had ever been there. The last thing to make it through before it shut up entirely, was a lingering, feminine moan of pleasure, a farewell to the dawning sun.