I can't promise to understand everything that the Ascendio mod does to Hogwarts Legacy, but it apparently tweaks the game's engine parameters to make it run better. Hogwarts Legacy has a stutter problem due to the way it handles shaders. Whenever you enter a new area, it has a tendency to chug and plummet your fps. The Ascendio mod, created by a Skyrim modder, does its best to fix that.