You deftly select the green vial, and decide to give it a whiff. A pungent smell of pine needles assault your nostrils.
"Go on ahead, try it", Rose encourages
Gulping the whole thing down in one shot, you wait for the strange potion to have an effect on you.
Soon, you have the oddest sensation. You at once grow taller, with your arse beginning to extend...backward? Newfound legs grow beneath your elongated body, as you realise you are turning into a centaur! Reddish brown fur begins coating your new horse body, while newfound muscles make their way all across your body.
There is also a rising surge of horniness as your dick begins to telescope into equine dimensions and your balls expand to the size of grapefruits.
"Well, that looks like an excellent transformation!" Rose comments. "Why don't we test out that gorgeous new cock you have?"