"Today's challenge"

Wanted to do something with a low bit of supernatural/sci-if element.

Here's the pitch:

Cassie is ending her high school career and is preparing for college. She's in the top 10 percent, has a couple friends but is also very reserved and doesn't socialize. People know her but can't recall much about her.

One night she has a dream she's had before: showering alone in the locker room while the other girls in her class shower around a big circular shower. The Dream proceeds much the same with her looking over at them but not going over.

However, this time, someone joins her. She can't tell who they are or even what gender but the person chastises her for hiding away from everyone and not satisfying her desires. Cassie tries to argue but the person touches her and she suddenly feels a burning need to cum. The person then tells her that if she wants relief, she'll need to satisfy a challenge (and a seemingly simple one, maybe get her first kiss or buy some skimpy lingerie) She won't get to cum otherwise.

With that the dream ends and Cassie wakes up and finds her hand down her pajama bottoms, fingers slick from playing with her self. Still feeling horny, she tries to pleasure herself but finds she can't climax. No matter what she tries, she just can't.

As the day proceeds, Cassie can't fight it anymore and decides to do the challenge, which immediately gives her an orgasm upon completion (possibly turning the seemingly innocent challenge into something far more erotic (sales person can't believe she just came from buying lingerie and seduces her, for example).

That night, a different dream occurs and a new challenge is added.

Is it all in Cassie's head? A demon? A device which lets someone enter her mind? Or something else? And what misadventures will she get into while trying to figure it out?

I like it! I love "transformation" stories, where someone gradually conquers a demon and becomes a better person in one way or another. Personally, I would never reveal the source of the dreams; let the reader fill in the blank. The struggle to obey them is drama enough.

I agree though I thought I would be fun if she thinks it's someone she knows and accuses them, is proven wrong and ends up having sex with them or engaging in some humiliation play.

For example: taboo

Mom: had access to her whenever she got a challenge, has seduced young women before including a classmate, and is working on some fringe science for the government...and quick look at her browser history reveals a mind control fetish.

Daughter decides when she gets her new challenge (maybe to masturbate in the same room as someone else) that she'll go ahead and make her mom get involved and then accuse her. For example, as soon as she and mom are alone in their room she starts openly masturbating in front of her mom and even draws her mom's attention to it.

Mom however acts completely shocked. When they both calm down and Cassie has her orgasm, mom wants to take her to a therapist or get her admitted temporarily. Cassie quickly spins up a story (mostly true) about feeling so pressured to not explore her sexuality or outwardly act sexy that she just popped.

Mom buys it and adds in apologies for keeping her daughter so sheltered while also being so brazen with her own pursuits. They make up and mom offers to let her use her toys. A guided masturbation session occurs and then the two of them have sex. Mom then suggests some light sub and dom play so she can supervise her daughter's exploration. Daughter, exhausted thinking her night time challenges are at an end, agrees and snuggles up with her mom...though she leaves a camera running just in case.

...only the challenge giver is still there, congratulates her and then tells her she'll have to work extra hard with two masters. Daughter wakes up the next morning and checks the camera. Her mom never left her and was asleep the whole time.

Non-taboo:

Girl made an enemy of a self-proclaimed witch at her school. When the challenge comes down that she needs to give head to a classmate and the first person she sees in the bathroom is the witch, she thinks she's got her number. She goes down on the witch but is very rough, fingering and spanking her even through her orgasm and afterwards. Then the rest of the coven come in and find her and she winds up having to service all of them. The coven invites her to come along to their next meeting for some more sapphic fun. She agrees but asks that they take the spell off of her.

"Wait, that actually worked? Wow...umm, okay, we'll take away your athlete's foot...though they sell cream for that too, you know."

Sure enough, that night she gets a new challenge while the challenge giver laughs it's ass off.