Be careful what you wish for.
"I hope you fall into a bag of dicks!" - A really rude curse
Plaenovdix, the result of a horrible cosmic joke, is inhabited usually by one mortal at a time and the lord and ruler of Plaenofdix, an Ovi'Tae by the name of "Richard Erectus Dangledong", or Dick-E for short. The plane is a pocket dimension that has a breathable atmosphere for the mortal that finds themselves cursed to this place. Generally, an individual spends only a single length of time equivalent to their sleep cycle in Plaenovdix, and awakens thinking it was a horrible nightmare.
The result of errant and idle cosmic thinking, two of The Ovi'Tae were observing a pair of mortals in a heated argument one day. One of the mortals said to the other "I hope you fall into a bag of dicks!". One of the gods said to the other, "I wonder if such a place exists". "You mean a bag of phallic objects to fall into?", said their friend. "No", they responded, considering carefully, "an actual bag of dicks one could find themselves fallen into."
This thought process wildly regarded as the most dangerous line of thinking amongst the gods. Considering if a place could actually exist, generally makes it so. And Plaenovdix, a small pocket plane in Eleriwen, was created.
Dick-E is first of The Bag Men, a horrifying creature of shadow and terror. The gods that created The Bag Men used Dick-E's capabilities as a template, but thought adventurers wouldn't be as scared of sharing their members if they were in on it, so they made The Bag Men malevolent. Dick-E spends his days and nights, toiling at his thankless task, which he bemoans loudly and often. He exits a Bag of Holding or similar extra-planar storage space, uses his mythical 'Bonercloner' on an unsuspecting victim, and sends a perfect replica to Plaenovdix, eternally adding both length and girth to the space.
Should a person ever be cursed with the phrase "I hope you fall into a bag of dix" (the spelling is important), the next time they find themselves entering a Bag of Holding or other extra-planar storage space, they will instead find themselves transported to Plaenofdix, forced to suffer the horrifying reality of their curse. 8 hours later, they will awaken outside of their point of entry, believe the experience was a horrible nightmare or hallucination, generally never decide to speak about it out of profound embarrassment or shame, and continue with their life. Once they've experienced the curse, they are immune to the effects for a period no shorter than 1d8+5 years.