Harry Potter: Cultivating Immortality in Slytherin

No harem + one-on-one romance. The Order of the Phoenix isn't villainized.

When a cultivation prodigy transmigrates to a magical world, he uses scientific thinking to reconstruct the underlying logic of magic. Lin En transmigrates into a first-year Slytherin in the same year as Harry Potter and binds himself to a cultivation System, only to find himself stuck in a low-magic world without spiritual energy. While others wave their wands and chant spells, he takes notes: “Levitation Charm energy loss: 67.3%. Can be optimized.” While The Chosen One studies the Standard Book of Spells, he writes The Theory of Converting Magic Power into Spiritual Energy. While Malfoy boasts about his pure-blood status, Lin En studies the defensive runes on a basilisk's scales. When Dumbledore talks about the magic of love, Lin En calculates the resonance frequency between the Patronus Charm and the Primordial Spirit's exit from the body.

He uses alchemy to upgrade potions, transforming Felix Felicis into “Enlightenment Pills.” He replaces spells with talismans, one lightning talisman doing the work of ten Confringo spells. He strengthens Hogwarts with formations, turning the magical castle into a sacred cultivation ground. When Voldemort's Avada Kedavra comes flying at him, Lin En raises a hand and activates a composite defensive formation. “Curse analysis in progress. Countermeasure generated.”

Dumbledore looks at him with keen interest. “What are you striving for, child?” Lin En pushes up a pair of imaginary glasses. “To test whether reconstructing magic with a cultivation system can prevent tragedies and reach the ultimate truth of magic.”

Years later, the heat from Hogwarts' artifact-forging furnaces mingles with the steam of its potion labs, as students flying swords and Quidditch players on broomsticks race side by side across the pitch. Lin En smiles at Hermione beside him. “The experiment worked. Time to publish the paper: ‘On the Feasibility and Practical Methods of Integrating Cultivation Civilization with Magical Society.’”