He’s about to have everyone mad at him with his cockiness: bragging that he wrote this blindfolded (see: with one hand behind his back, and other expressions of superiority).
Also a pun on the title of this song, because blindfolds make it dark, and also are part of certain ‘twisted’ sexual fantasies
Suggestions
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As Rayneman said, though I would add that the mention of his knuckles indicates that those scars weren’t merely inflicted on him, but were earned by fighting for what he believes in.