This story is a sequel to Gifts from a friend
All Fluttershy had ever wanted was to be a good friend to the girls, to take care of her animal friends, and to have tea with Discord. She never thought those things were bad, for anypony, and she certainly never thought they'd be weaponized against her.
But the nightmare is finally over.
Or so Fluttershy hopes.
A commissioned sequel to Gifts From A Friend by Element of Malice, written as part of a special commission drive to support our friend, Luna.
Chapters (1)
So i think the sleep paralysis demon is probably discord because it could read her thoughts, so once she willed discord to help her, he knew he should show up (and it had yellow eyes)
other than that i didn't understand what is happening even after reading closely a few times
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As linked to twice in the long description, this commission was requested as a sequel to another user's story. For better context for this, I'd recommend reading that first.
I’m glad to see that it finally made it onto this site.