Halloween Horns is an explicit adult transformation illustration by KannelArt — a devil costume that stopped being a costume, on the guy wearing it.

Story: The inset panel is him mid-change, teeth gritted and blushing as it takes hold. What's left afterward is real horns where the headband used to be, a real tail curling up over a plush new ass, and his whole body reshaped into a woman's — down on all fours, looking back over her shoulder like she already knows none of this is coming off after tonight.