Out of all the changes Blizzard has made to Diablo 4 since it was released two years ago, its most basic dungeons have gone largely untouched. A few things have been tweaked here and there, but they've largely taken a back seat to all the new dungeon types introduced after launch.
In Diablo 4's next season, dungeons—specifically Nightmare Dungeons—will have a purpose again. Instead of an activity you do as you're leveling up and then forget about for the next 50 hours, Nightmare Dungeons will be the source of most of the crafting materials in the game, and, of course, they'll also have opportunities for valuable loot.
