Not Rat, Not Weasel, and Nothing In-Between
My own headcanon for what Razzid Wearat really was. I know he's called a "Wearat"--and rumored to be this hideous rat-weasel hybrid crime-against-nature... but uh no! I prefer the idea he was simply an animal from a bit outside the usual Euro-centric cast of species which the locals were terrified of since they simply didn't have any kind of idea what it was. Similar to how human beings "chimerize" their descriptions of unknown animals (example--describing a binturong as a "bear-cat", believing it to have a bear body and a cat face, or some mix of features despite the binturong being neither of these), the "Wearat" would be more accurately called a Moonrat--or a Gymnure. The Moonrat/Gymnure is actually a close relative of the Hedgehog! Physically it has a clearly carnivorous face and dental structure much like a hedgehog or a shrew (the "weasel" aspect) but form-wise is a bit more rat or really opossum like. The intense "ugliness" is really a matter of subjectivity--they're really not much different looking than moles and shrews, so... XD
Pictured is how Mossflower residents typically only see the Moonrat--in the form of a long Corsair, ranging far and wide from their homelands as part of a pirate crew--likely driven out of their own community for their willingness to pillage and exploit, much like how I envision most Corsairs, Sea Raiders, Searat crews and the like are.