#...er

In fact, as I mentioned in my post on some of the game's unused assets, the Duke actually has a number of unused voice lines that seem to relate to him selling Ethan more information (“You won’t come across this information just anywhere,” “A little bird whispered this to me,” and “Not to presume, but some advice if I may.”) ‒ possibly treasure photos or hints to significant locations.

Fortunetellers and other folk who offer cryptic-yet-vital advice are a regular feature in horror stories too, not just fairy tales. If offended, their role can easily overlap into that of 'witch', for greater monster cred. But for my money, the Duke himself doesn't come across as the easily offended type, so expanding his role into 'monster' might be reaching.

Alternately, you could also look at the villainous Masked Duke from the Shadow of Rose DLC. I doubt he much resembles any authentic 'original' plan for the character, and he's very much his own entity, but he's certainly an effective villain.

(Though if neither of those work for you, given the Duke's size and association with food, 'literal giant who eats people' might also be a fairytale archtype that could fit.)

All that said, I do wonder just a little if there was ever a plan for the Duke to have a proper villain-reveal moment, when you learn he's the fifth lord. I have this whole semi-developed theory that the Duke is actually working on Miranda's direction for most of the game we all played: after all, she seems to want Ethan to destroy her 'false children', and it's the Duke who sets him on the path to do that (with some input from the old hag, our other cackling-fortuneteller-character). It's only once Ethan wakes up in the Duke's carriage at the very end that he unambiguously picks a side against Miranda. After all, even if he was always privately rooting for Ethan, why stick his neck out for a man who might not even survive the day? That's just not good business.

But even if the Duke wasn't working for Miranda from the start, how much do we really know about his motives? It's far too easy to read his eagerness to buy the crystalised remains of mould-infected individuals as the stuff of war profiteering. How much would the additional remains of Miranda, and even Ethan, be worth to him? And these are hardly the only possibilities for what he could really be after!

In short, I would actually love to see more villainous takes on the Duke. Don't get me wrong ‒ I do love that a character as shady as him doesn't turn out to have been Evil All Along, but he's still sinister enough that I'm intrigued by AU possibilities where he has his own twisted plans for Ethan all along, whether as part of Miranda's scheme or all his own. There's stuff you could do here, I'm just saying!

One one final note, people have suggested the owl crest you can see in the background of his shop and the carpet of his carriage was intended to be the crest of his house, and that seems broadly plausible (more on that & translations in my post on everything we do know about the village lords). While I'm at it, have some high-res versions of both from the game assets.

I'm sure you don't need me to tell you that an owl represents wisdom, or how that tracks with his role as a source of information for Ethan either.

Does it actually look like the crests of the other lords, though?

Eh, a little? You'd have to do some heavy reworks to make it fit in a diamond like all the others. As for overall shape, you could even say it bears more resemblance to Miranda's crest.

Does that mean anything? Eh, if you want it to. Who knows?