The party upstairs was in full swing, the bump-bump-bump of the music audible even from outside.
In the darkness on the back stairs, a shadow moved. The form had almost no shape; it moved like liquid. It climbed each step with meticulous care, coalescing itself before pushing its turgid form upward to grab the lip of the next step.
As it climbed, it left an unbroken strand of itself behind, a connection to something as yet unseen in the gloom beyond. Its progress was slow, but inexorable.
It reached the summit and paused, gathering itself and pulsing gently in time with the beat of the music inside. With each pulse it grew, siphoning more of itself upward until it filled the landing.
The span of a human heartbeat — and it surged under the door with alarming speed, invading the space within. What moments before was a festive celebration took but moments to dissolve into terror and screaming.
The screaming ended far, far too quickly.
Originally posted on Ficly.