I think this would make a nice basis for a curse, to tie a group of people together and bring them all down.
A Rat King is when several rats get their tails tangled together in knots, and die trying to get out. They cluster of corpses that remains, when found, is called a Rat King. The rats try to chew themselves free by biting the tails of the other rats, and they all fight back, tied together, in what must surely be a horrible way to go.
Using a rat King as a basis of a curse is a great way to target an organization or group of people at once. The parallels between what a Rat King is and what you want to do with this curse are just too sweet not to use.
A Rat King is such a novel and unique thing, it doesn’t even require a sigil to represent it, the very idea is it’s own sigil. Although some tied together rat tails representations wouldn’t be out of place.
No real recommendations on how to use this in a curse other than a Rat King is a good place to start. If you could get your hands on a real one to use, that would be awesome, I know I’d like to find one. But the idea it’s self is strong enough to stand on it’s own.
I’ve taken precautions to protect myself and my peeps from any Rat King based curse, as well as from any other magical shinannigans. Just in case anyone gets any not so bright ideas. An unfortunate necessity when posting curses online it would seem.