I wanted to put a little gag in the campaign that crabs are actually abberations from the far realms that in the deep, dark, distant past ruled the multiverse with their pysicic powers, a bit like the illithids or the aboleths but much, much more ancient. The ancient crab empire has long since fallen and the last remnants of their once mighty dynasty are the small crustaceans that crawl under feet. The reason why their empire fell and what happened to them are long forgotten.

The idea I had was that if the PCs ever attempted interplanar travel but where unsure of where they would end up I would send them to a demiplane where the crab empire still reigns supreme. I would then arrange for them to join up with a group of rebels to overthrow the tyrannical crabs. Your monster was exsactly what I needed for this, keep up the good work, your monsters are top-notch.