2) Branching off the above prompt - Pick a fandom and set one character as the monster under the bed/in the wardrobe --Gallifreya
Every child gets a monster. An ancient contract, written in blood. Paid in teeth. They stay until the child is strong enough to care for themselves.
Some... never leave.
They are the monsters for the people who are particularly vulnerable. The people with one foot each in two worlds. The people who are open to specific influences. The people who sense slightly more than the average person on the street. The people with a little bit of magic inside them... but not enough to protect themselves from the things that would prey on them.
Monsters keep the faeries at bay.
Humans have everything backwards, of course. They've forgotten the old tales. Bent and warped them beyond recognition, turning the fae into friendly things just because they are pretty. But if you look deeply into the old takes, the ones with the blood still in them... you will learn.
Faeries are glamorous, they create glamours.
Faeries are wonderful, they make wonders.
Faeries are terrific, they beget terror.
Children tell other children without ever knowing what they're passing on. In ancient rhymes and silly games.
My mother said I never should
Play with the faeries in the wood...
People forget. Rhymes never do. And the monsters have not forgotten, either. They are the reason why the people have forgotten. They are the guardian in the dark. Steadfast and silent. Watching. Waiting. Making certain that those who would come to steal and use never do.
They are the things that go bump in the night. And they are there for your protection. If you hear them, or see them moving doors without you... feel free to thank them.
A little thanks goes a long way.
Frisk woke in the middle of the night to their wardrobe door creaking. The sudden adrenaline rush triggered some nightmarish memories... but the smell soon banished those. They were no longer in the Home. The redolent perfume of bakery was better than incense and chanting for dispelling those demons.
But all the same... something was in their room.
Frisk, pretending to be asleep, rolled over and cracked an eyelid to scan their room for intruders. The windows were shut. The curtains didn't rustle. Everything was put away neat and tidy. The night lights lent enough illumination to see where everything was. And nothing initially seemed amiss.
Except for the wardrobe door.
It was, as Sans might say, not a door any more. Because it was ajar. And as Frisk watched, it edged closed, just a little bit.
Frisk quit pretending to be asleep. They crept up to the wardrobe door and thrust it open to discover a monster.
"Have no fear, Human," said Papyrus. "I, the Great Papyrus, am guarding over your dreams tonight! You will have the soundest of slumber, and the sweetest of dreams! I guarantee it!"
Frisk sighed, rolled their eyes, and went back to bed. Monsters had a way of solving the wrong problems completely backwards, but also the exact right way. Before they got comfortable, they signed, Announce yourself, next time. You scared the beans out of me.
A gloved hand gave them a thumb's up.