You think Abbie would make a good demon of temptation

You grin at you sister. “How would you feel about being a fertility goddess, Abs?” you ask her. “I could keep you knocked up all the time, and we’d have lots of little demigods running around.”

Her eyebrows shoot up at that. She clears her throat nervously before she answers. “I don’t know,” she says. Her hand moves to her toned belly. “I wasn’t planning on being a mom just yet.”

“Relax,” you laugh. “I’m just fucking with you. I’ve got a better idea for you.”

She swats your shoulder. “Damn, you’re getting better at lying. Or maybe it’s just easier to believe anything you say if you can make anything true. So, tell me, what’s your idea?”

“I’ll do better. I’ll show you,” you say.

Abbie grows small horns from her forehead. Leathery little batwings grow from her back between her shoulder blades and her spine. Her skin takes on a pale red tone. A long, snaky tail with a sharp barb on the end sprouts from the base of her spine. As long as you are making changes, you grow her tits and extra cup size, while keeping them pert and firm.

You manifest a mirror so she can look at herself.

“Wow! So, you think devil is a good idea for me? Nice way to think of your big sister,” She says with mock indignation. Something about her reflection catches her eye, and she leans closer to the mirror and opens her mouth to see the sharp fangs and long, slithery, forked tongue you gave her. She turns to you with a raised eyebrow.

“Yeah, you certainly tempted me to sinful thoughts,” you snicker. “I’m giving you powers, too. It’s not just a costume. From now on, you will know the deepest, darkest, most shameful secrets and fantasies of anyone you meet. You’ll have the power to either let a person indulge in their fantasy or punish them for it. Your choice.”

“Hmmm… I can see where that could be sexy, but a lot of it could be disturbing with a large side of ick,” Abbie says. She stares in the mirror as she speaks, trying to figure out how the fangs and snake tongue aren’t messing up her pronunciation.

“I’m sure you’ll handle it,” you tell her as you pull her into your lap. She shifts, trying to settle without her wings and tail getting in the way.

She smiles and leans into you, running her fingers up and down your chest. “It’s not like I have much choice in the matter if it’s what you want," she says. "I’ll learn to make it work for me.”

You hear a flutter of feathers then your mother’s voice from the living room. “People all over the world are frightened…” her words stop on her eyes go wide when she steps into the kitchen and sees demonic Abbie sitting on your lap.

“David! What did you do!?” she scolds. “Abbie’s your sister! Not some kind of toy.”

Abbie just stares at your mother, not answering.

“We’re just having some fun, Mom,” you say. “I thought if you’re going to be an angel on my shoulder, Abbie would make a good devil to balance things out.”

“This is going too far,” your mother pleads. “Just put things back the way they were.”

“You mean with war, sickness, hunger, and ****?” you challenge her.

“I know you’re a good person, honey,” your mother says. “But even the best person can’t handle this kind of power without being corrupted by it. Look what you did to me and Abbie. This isn’t normal.”

“Is it normal to dream about fucking your son, Mom?” Abbie asks in an accusing tone.

“What?” You ask, turning to look at Abbie.

Your mother’s face turns red. She stares at Abbie. “What do you mean?” she sputters.

“That new power you gave me showed me Mom’s shameful fantasy,” Abbie says. “She’s a lucid dreamer, and since you turned eighteen, she’s been dreaming about fucking you on a regular basis,” Abbie says, staring daggers at your mother. “And now that you can make anything you dream come true, she’s giving you crap about having some fun with me.”