....You're shorter. The witch was a few inches below you, one or two. But you're finding yourself looking up at her. She hms, somewhat contemplative. "Unexpected." She rubs your head, pushing you down a little more. It's a strange feeling, like you're being compressed. It's like a massage but a touch more forceful. You mmmf slightly as you look yourself over. You're still yourself, all your normal proportions, just naked, below five feet, and wearing a collar.
"What is unexpected Mistress?" The title for her comes out unbidden. It's weird how quickly you've accepted that. She's Mistress. It's just natural to think of her as that.
"That you're not becoming an animal like I thought. Hm." She doesn't sound annoyed or disappointed, just more curious than anything else. She looks you over, curiously. You look back at her. You feel a faint burning in your eyes, causing you to rub up at them as they water. When you drop your hands your Mistress is on you in a second, raising your chin to hers. "My goodness, those are *quite* striking eyes."
She lets you see yourself in the mirror. You still look mostly yourself, though you're pretty sure you're an inch or two shorter, though your hair is starting to turn a dark steel-silver color threaded with dark blue and your eyes are...different. They're inky dark, pure shadowy pits with no sign of anything else in there. They're faintly shiny and the darkest things you've ever seen, like pure darkness given form. "What am I?" This does weird you out, a little.
"You're a Shrouded Imp, pet, a creature from the realms of darkness. It looks like you had some infernal heritage that woke up when I made you my little pet~" She rubs at your head, giggling, one hand reaching down to pinch at your ear, sending a feeling of some pleasure through you, it's relaxing rather than sexual however, and you can feel her fingers drawing your ear out, the other getting the same treatment as you wiggle under your hand, losing another few inches, a shade above four feet now, now sporting a pair of long knife-like ears sticking out from your lengthening hair. "It seems you'll be my shadow, and will be staying in there when I don't have need for you. Which, coincidentally, is now." She snaps her fingers and you find yourself beginning to sink into something dark, warm, and comfy, sleep coming over you swiftly despite your best efforts.