I'm curious as to what this chapter means for power-scaling in this story, particularly when it comes to where Duke (the demon king) ranks, and if this is a retcon of earlier chapters.
While power-scaling has always been a bit unreliable to begin with in this one (and is admittedly not the focus of the story), we were told early on that Eve was supposedly stronger than Duke, and then later that Sophia was in the 'same class' as Eve, yet both were clearly no match for Lloyd. From this, I at least assumed that the the fight with Duke was difficult only because he had an army of demons with him, and even then probably ended pretty quickly.
Now we're told that defeating Duke (with no mention of the demon army) took three days of continuous fighting, suggesting that he was at least somewhat comparable to Lloyd in strength, and by extension significantly stronger than Eve (who appears to otherwise be the strongest non-'hero').
That said, our source for those early comparisons was the King and intel from the kingdom, so maybe they were just flat-out wrong and never understood how strong Duke really was.