I wanted there to be some sort of canon reason that Edwin keeps reaching absurd sizes in their weight, so I finally gave them some lore!

Monsieur Gloument (pronounced glow-MAWn) is a powerful trickster fae who likes trapping people and fattening them up before draining the fat off of them. It had a run-in with Edwin one day and realized that they needed no convincing to eat tons and tons of food. After revealing their true form (and intentions) to Edwin it offered a proposition: Edwin would be given certain magical boons that allowed them to always find food and eat as much of it as they want, but on every new moon Gloument would visit them and take half of their body weight away. Gloument made sure to explain that it'd prefer to only take away fat, but if there wasn't enough fat that they'd just as gladly start taking away at Edwin's muscle and even bone mass.

So yeah, in D&D terms Edwin is a fae warlock, but all of their spells are things like "Instant Digestion", "Shrink Self", etc. And their pact requires them to gain plenty of weight so that they don't suddenly become a mummy on the new moon.