Porrigo

"Porrigo!" He exclaimed with excitement, a grin on his face that quickly died and became an expression of fear as his cock began to shrink, shrink and shrink "Finite incatatium!" He shouted, but it was too late.

Instead of the 2 inch dick he once had, he now had a 1 inch dick, tinier than his own balls. Grabbing the page with the spell, he read the warning.

"Porrigo, this spell will mold your cock as if it was made out of rubber, it will first shrink down to 0.1 inches, before growing and growing and growing, it will be stopped once the user castes the finite incatatium charm, but be very careful, as this spell is irreversible, the size you end the spell in, will be the size of your cock for the rest of your life."

He felt his eyes start to fill with tears as he realized he had now cursed himself with a dick that was half the size of his original dick, he wondered if it could even be considered a dick at this point, it was so tiny that it could easily be dwarfed by a 5 year old. As Ron stood naked, the door opened.