To me, the feeder villain trope in partuclar can by either someone who wants to fatten up the entire populace for their own purposes (like, for instance, cooking them and eating them as seen in a Super Nintendo entry in the Super Chinese series, which thankfully ditched the reused Super Mario Bros. sounds heard in the NES installments, or forcing them to stay fat forever as seen in Tengai Makyou: The Apocalypse IV where a villainess known as D sends out her henchmen to fatten up everyone in Arizona until her eventual defeat), or as a way to interrogate someone or lure someone into a trap (as seen with the first of the last five episodes of Kirby Right Back At Ya! where the secondary protagonist was kidnapped by King Dedede and was threatened to be force-fed if she didn’t tell him where the Warp Star was hidden before Kirby and the protagonist’s younger brother came to her rescue, or a comic by the DeviantArt user Saxxon involving a superhero who becomes immobile after binge-eating on her weakness, donuts, before the villainess of the comic is shown in pre-recorded footage where she force-feeds the hero’s sidekick before she spills the beans on the hero’s weakness), or even as a way to silence someone (as seen with, and I get nightmares just thinking about what might have happened rather than what actually happened, the Totally Spies episode Passion Patties where Sam and Alex become tied up in chairs just like Clover as Dr. Bittersweet tells them her plan to take over the world using a combination of the cookies’ fattening effects and the money made from the cookies’ sales before she decides to silence the trio with a method of execution she calls “Death by Cookie” before the spies themselves escape and take the still-addicted Clover with them).
Whatever the motivation ends up being(since the antagonist is the feeder from the sounds of it), here’s hoping there will be plenty of content for black hat playthroughs(aka deliberately fucking over the Protagonists and letting the villain have their way with the world).
Considering the mention of capture and guilds, I could see it as a method of sabotage (both by reducing the food supply and the physical capabilities of the people). It could come from a rival guild, or perhaps somebody who might peace by rendering everybody equally incapable of fighting. Inducing dependence in order to fulfill the villain’s personal need to take care of/nurture people
Alternatively, this might just be an aspect of some greater process, perhaps like restoring an ancient, bygone civilization where overweight physiques were venerated. The villain might not personally care otherwise other than it was an aesthetic of their old civilization (if an immortal type) or one they admired. In the opposite temporal direction, a time traveler from the future might have an agenda that depends in part on changing society in this way.