[Max-level combat classes, invincible, handmade magical industry, prince, maids]
After maxing out every combat class, Luo Lin transmigrates into the body of a prince with an intellectual disability in the Middle Ages. From the start, his stepmother, the queen, abandons him in a cursed frontier town to die. Beast hordes descend every winter, and he faces one crisis after another. Though the cursed townspeople can never leave, each of them has the innate constitution of a mage, even if they can’t use magic. See how the prince puts cheap magical laborers to work creating magical industry, including arcane cannons, and keeps the town safe. Mages: “Wind magic is a cutting machine, fire magic is a forge, water magic is a pump...” He makes paper, soap, soda, maid outfits, lace, and white sugar by hand, builds a commercial empire, and becomes the greatest lord.
It's so cool to restrict you when you're invincible.