While obscene is a matter of perspective, I had KK indulge a particular speculum play fantasy at a dungeon event we attended a few years ago.
With her ankles bound to a specialty upholstered horse, I lubricated her pussy, and inserted a metal speculum, to dilate and open her, leaving her gaping, exposed, and vulnerable. I had her masturbate, stimulating her clit, while numerous men masturbated themselves over her stretched, gaped-open pussy, one after the other, ejaculating into her. Me, along with a collection of men filled her pussy with cum until she was overflowing, cum running over the edges of the speculum down her ass, over her belly, while she watched us and buzzed her clit to orgasm after orgasm.