The grind in Diablo 4 begins in earnest after the campaign ends. The main story is a tutorial. The real game starts when you unlock Nightmare difficulty and see your first Sacred item drop. Suddenly, every piece of gear you own is obsolete. You need to farm new weapons, new armor, new rings. This reset is not frustrating. It is liberating. The game has given you permission to start the hunt all over again. And the hunt is the best part.