"The worst ring possible" is the description of the Pumice Ring, which like most rings has random stats so quite easily could not be the worst ring possible. (It is still a low level ring so generally it won't be great)
It's actually the worst ring possible because it's cursed -- once you put it on, you have an insatiable desire to collect lutefisk to sacrifce to the lutefisk god. Oh, and it gives you an itch right on the part of your back, under your armor, where you can't reach. And it gives you bad breath as well (or maybe that's just me).