It would be awesome if someone would write a story based off the anime Oh! My Goddess!
My basic idea is that Hild convinces her daughter, Urd, to become a demon. The two then abduct Urd's sister, Skuld, to make in to their new slave and force her to clean their dirty, sweaty feet. Skuld refuses at first so the two decide on a way to torture her until she agrees. In the original manga it says one of the worst torture for a goddess is to be tickled, so both mother and daughter tickle the goddess' feet until she agrees to clean theirs.

If you need pics for reference just ask me.