The Hollow Man Knocks Twice: Dawn of the Eldritch.

Harold is nobody. A washed-up thirty-something drowning in dead-end jobs, cheap beer, and a hoard of useless junk he impulse-bought from late-night infomercials. He doesn't believe in magic, gods, or anything that can't be explained by bad luck and worse decisions. But something has been watching him. Clinging to him. Something that a girl on the edge of a bridge can see.

Lux doesn't die. She's tried. More times than she can count. But every attempt-every reckless plunge into oblivion-ends the same. The universe refuses to let her go. So she does the next best thing: she starts calling to the things lurking beyond the veil. And something answers. Something that knows Harold by name.

Now, the two of them are caught in the pull of something vast, ancient, and hungry. A force that doesn't kill, but replaces. That doesn't take souls, but rewrites them. As reality itself starts unraveling-as neighbors vanish, time loops, and shadows move wrong-Lux and Harold must uncover the truth before they become just another echo of the Hollow Ones.

Some doors shouldn't be opened.
Some people were never meant to exist.
And some things are already inside.

Contains mature themes. Reader discretion is advised.
I will take inspiration from real-world religions and mythology but will appropriate it for the sake of the story. If any being acts in a way that is untrue to their real-world counterpart, it is not a mistake.
The cover is from Vecteezy, here is their attribution thing:
<a href="https://www.vecteezy.com/free-videos/hotel-hallway">Hotel Hallway Stock Videos by Vecteezy</a>