Haha, yeah. I played through the first time completely innocent of anything, so I didn't even know what thief's ring was. I tried using graverobber's ring, because I wasn't sure if those manta rays were technically "black phantoms."
I also was encumbered the whole time, and didn't know there was a faster roll out there.
edit: I just figured out that I won't be able to get to Black Phantom Garl Vinland on this playthrough. I was hoping to get down to -6 tendency, then kill BP Selen and the primeval demon to shoot it up to full white, but you need full black for Selen to show up, so I will be one off. :/ I suppose I should have just planned better to be able to reach everyone.