With a Signet ring, that is a cursed piece of clothing.
Viewing post in Ero Dungeons [Complete] comments
Important to note that you can't upgrade the rats. whatever level the cursed ring is that you get to force your character into a rat/slim/goblin/whatever it will always be that level and no further skills or progression on them will upgrade the class nor give you more fighting options. Which I find really sad actually.