Comments posted to our Dark Souls 3 Wiki
Why tf does a moaning knight (aka Eygon of Carim) have this??? Well im glad you asked (let's pretend you did, ok?)! My best guess is that he gave it to Irina so she'd have a better chance to become a firekeeper but it had quite the adverse effect, making her vulnerable to those little creatures nibbling her flesh (because it makes the wearer vulnerable to Dark and my best guess is that these things are affiliated with darkness).
This is actually a really good theory.
"It should be noted that the Blindfold Mask when not broken, gives -30% dark defence, while a Broken Blindfold Mask will give -15% dark defence, the attack buff will remain the same. (A streamer told me and showed me the comparison if you need evidence.)" This is not true, this is mearly a display error on the game's part.
On my dark sorceries build, with dark clutch ring, two dragon rings, scholar candlestick WA + izalith staff +5 offhand WA and 45/45, Great Soul Dregs do ~1150 damage on dancer, but with Blindfold Mask added they do ~1500. Meaning there are some sources of increased damage this mask scales with multiplicatively, or the mask lowers enemy resistance instead of increasing player damage.
dancer just has trash dark resist is all...
What about dark arrows?