NPC Criminal Dyer at Whispering Caverns.
Players who are criminals, currently, have no way to have access to the dyeing mechanic, as dyers only spawn on merchant ships and are only willing to talk to neutral/positive renown players. This can easily be solved by adding a Criminal Dyer NPC that only exists in a fixed location.
Why choose Whispering Caverns as the location? Currently, it has no major purpose and is fairly insignificant aside from the occasional criminal/hero and the underwater maze. Adding an NPC would increase its importance and make it more useful as a location.
To counterbalance the fact that the dyer will have a guaranteed spawn at Whispering Caverns, the prices will be marked up by 200% (3x the price of normal dyers) and the Dyer will only come out (spawn) at night.
Also, from a lore perspective, it would make a great criminal hideout, because it is an (or at least seems to be) abandoned fortress, and food also naturally grows there (the giant mushrooms). It would make sense for a criminal to hide there and conduct their business without getting arrested.