Haunts of the Slitherskins

Just keep going, you little brats, and I tell you... the Slitherskins will come get you in the night, drag you away, and you'll never be seen again!

— Frustrated nursemaid of the Sovereign Isles

Summary

The Haunts of the Slitherskins isn't so much a single tale as a collection of related folk tales all centered around misbehaving children being punished by the mysterious 'Slitherskins'. Though the tales are diverse, they typically focus on halfling or human children who refuse to obey instruction given by their parents. Older versions of the tales focus more on children refusing to stay within sight while out playing or staying out far past their curfew, but more modern iterations of the tale have branched out dramatically to include children (including dwarven and elven children!) who refuse to do their assigned chores. Almost universally, the subject of the Haunt is a precocious
A typical Slitherskin Haunt goeth thusly:

• A precocious child, beautiful and cherubic, is the absolute darling of their parents' eyes. The child not only can do no wrong, but simply doesn't do wrong because they have been properly raised to be a good member of society
• All of a sudden, things change and the once cherubic and proper child starts acting out. They refuse to do the chores they had so faithfully done before. They come home far after curfew, when even the sunset light has dipped below the horizon. The parents realize something is amiss, but do not act immediately, for how could their child be at any risk? They simply believe it a short phase the child will grow out of.
• Then, one day, the child never returns from playing with friends, with scraps of their clothes found on the riverbank. Or, alternatively, after a great fight with the parents, the child goes missing one night from their bed, the sheets torn into shreds, and the window left hanging open. They have been abducted by the Slitherskins, never to return home
• The parents grieve, for they have lost their once-perfect child. The child's friends grieve, for they encouraged the rulebreaking. The town grieves, for nobody had listened to the moral of the Slitherskin Haunt and yet another of their precocious younglings has gone missing.

With such a tale told, it becomes clear what the moral is for misbehaving children: obey your parents and be a good child, else you be spirited away by the awful Slitherskins, never to be seen again!