Lots of things I don’t know about the hidden aspects of that Spider Anime, but i keep wanting a scenario where the traitorous adventurer guy makes a bargain with the spider demon lady for power, but doesn’t know his end of the bargain.
She poisons him with a string paralytic, magically forces him erect and rides him like a stubborn pony. Then when she really gets into it, she uses a series of webs to puppet him into fucking her.
Trauma and steel-web wrist scars aside, he survives this, and then some time later when he’s back in ‘friendly’ territory, he receives a sort of magical thank-you card depicting all the spiderlings he’s conceived. Gets the title Father of Spiders and gets ridiculed by everyone who sees it, besides monsters themselves whose reactions range from ‘kinky’ to “What you doing later?”.
All this being a side benefit to the demon, who’s actual benefit was being able to lay an egg that will serve as a rebirth point. Leading to an extra-traumatic event where the traitor will be treated to being called ‘Honey’ and ‘Dad’ by the same person.