"You... you what?" Kas balks, looking rapidly between your face and chest. "No, I can still sense it, I can damn well smell the soul on you! What do you mean you don't have it anymore — you're no demon!"
"I'm not," you say, "but I did give my soul to one of the Seven. It's just a placeholder you're sensing, something to fill the void."
The demon queen's eyes harden, and her hand plants itself open-palmed on your chest. "How... but I can't sense... it's even still growing! Marae's tits, it's just a fucking reflection, isn't it? How could I be so dense!? How could I have thought you..."
Kas snarls, standing up so suddenly that you're nearly thrown from the couch. "Damn you, Phaere. Damn you to the deepest depths of the void. Your soul was my only chance... the first real chance I've ever had, you damned fool, and you threw it away for what!?"
"So what if I did?" you shoot back. "It's mine to give away, not yours to take."
An open palm crosses your cheek hard enough to make the couch rock under you, nearly spilling you over the back. By the time the stars have cleared from your vision, Kasyrra's winged back to the fireplace and has her hand on her axe, stopping just short of lifting it. She's faced away from you, face bathed in shadows. "Get out," she snarls. "For the sake of whatever love I bore you: get the fuck out before I cleave that worthless head from your body! If I have to make war on the very gods of this realm to achieve my goals, then so be it. I will sunder the heavens and corrupt your damned Seven, just as Lethice did to the old gods of Mareth. I will not be denied!"
"Kas, wait!"
She heaves up the runic axe onto her shoulder, turning towards you with a fiendish fire burning in her eyes. "I cared about you; I would have made you the queen to rule at my side if you asked, and all I wanted... I told you from the start what I wanted in return. Yet you squandered it on a whim, for a being that will never care about you half as deeply as I do... as I did. No more. Go now, before my anger consumes me entirely. Go, while I still hold out some hope that the pale reflection in your chest might somehow be of use to me, someday. That your false soul will someday lead me to the real thing, wherever it may be."
No matter how strong you've grown, fighting the demon queen in her deepest lair is a losing proposition. You beat a retreat from the manor as quick as you can, wincing when the doors slam heavily behind you — followed by a howl of rage and desolate loss that promises to haunt your dreams for the rest of your life. A life that might well be cut short the next time you see this queen of demons.