Actually committing adultery in the mind--or in any form--is okay right when you hit 18. That's when you become an adult. So sayeth the federal government.
Invoking references to D&D, Lovecraft, Warhammer, and etc. is perfectly alright. There are no nerds here, only repressed, angry, young adults who await Cthulhu's coming. (It is okay to make these references if you're not familiar with the world, have never read/played it, etc. However, if you sound like an idiot upon making the reference, ridicule is an appropriate punishment.)
Rule 34 must always be called to sate your lust, even if you really don't want to see it.