Narrate a flashback to your childhood that shows the first time you encountered a dark entity.
[TW: self injury]
The shades have always been there; for as long as he can remember they've lurked just at the edge of his vision, slipping away when he makes any effort to focus on them. For as long as he has seen them, no one has ever believed him when they ask why he's so distracted by nothing - writing him off as strange or even unsettling.
He knows that his peers want nothing to do with him, that his sisters only tolerate him, that his father cannot stand him - he knows, above all, that he is entirely unlovable due to some deficiency, some flaw in himself from which he is entirely inextricable. It is an isolating childhood and it is one that hollows him out slowly and completely.
When he first takes a knife to himself he learns two thugs: that there is a measure of relief in the action that he does not want to admit to himself, and that this is what it takes to draw one of the monsters from the dark.
It lurches from its place in the shadows to crouch before him, its body a mass of twined and knitted tendrils of shadow - eyes peering at him from between any gaps in its ropy form.
We have waited for so long, it says, voice the hiss of wind through a bare tree. There's almost a reverence in its tone, a hunger that he cannot yet name. You have much to learn yet.