Stray Insanity
...seem to be.. broadcasting from another dimension and cannot hear me ...
rofl rofl rofl
on topic: i have noticed a few things, so bear with me as well. it appears to be that some rings will drop in different areas more frequently than in other areas. the frequency seems to depend on the necessity of the ring. for example: iron (a buff that prevents enemies from putting you too sleep or catting you) drops for me in Shallow Seas when i fight queen lorelei, at the EB fight in the Sea Lab Compound, or when fighting masks in Otami Ruins. (this isn't the only ring drop i get in these areas, but i get them "more often"
wink
i would, based on my theory, assume that "slash" would drop in areas where animated are most like to mob. for example: the bootsnakes in deadman's pass or outlaw pups in bass'ken lake or tiny terrors in otami ruins. again just a theory, but using "luck rings" and "luck ringsets" may improve the odds of dropping the ring you need to complete your rings.
there is also a quest ring reward, in beating End Boss for the first time. if you get the quest asking you to save Marshall in SS, then attempt to fight and win the EB battle (even on easy) you will receive the ring reward option where you can pick the last of the rings you need. (you would have to go to Barton's Bar, speed through the talking, and get the option before leaving. if you accidentally exit the bar, you can always run back in, but you have to finish the conversation part). Ps. you can't leave a smeb crew before going to bar or you won't get the ring option.
tl;dr = GL