Diablo 4 Sacred items are special pieces of gear that are stronger than your usual normal, magic, rare, legendary, and even unique items. That's because Sacred is a term that can be attached to any of those item rarities, making them better than the regular old version you'd usually get as loot.
Speaking of powerful gear; crafting Legendary items is a great idea if you're struggling with the campaign, and upgrading your healing potion can help, too. Either way, here's how to get Sacred items in Diablo 4 and what exactly they are.
How to get Sacred items
First thing's first: to get Sacred items you need to be on world tier three, i.e. Nightmare. This means you'll need to complete the campaign and finish the capstone dungeon in Kyovoshad's cathedral. After that's done, you can change your world tier at the statue in Kyovoshad's main square, which unlocks Sacred items as a potential drop.
While you can get Sacred items the same way as any other loot, the best method seems to be defeating elites in dungeons, as well as opening resplendent chests, and greater radiant chests. Since you can get Sacred items at every rarity level, some of the drops are definitely more useful than others. You'll know a Sacred item when it drops due to it saying Sacred in brackets alongside the regular name, plus the top of the item icon will glow in your inventory.
You can also purchase Sacred items from merchants and get them from Curiosity Vendors for Murmuring Obols—just look for which of the question mark icons has the Sacred glow to know which might get you one.
What are Sacred items?
Sacred items are essentially better versions of the normal, magic, rare, and legendary gear that you got in the Veteran world level, but you can also get Sacred unique gear, since unique items also unlock as potential drops in the Nightmare world tier. The key difference is that Sacred items roll higher stats than their regular counterparts, so are essentially just better versions of those same items.
Generally, I'd suggest holding onto Sacred rare gear for potential building and upgrading into legendary, while you can sell Sacred normal and magic gear, which seems to be worth a bit more than its regular version would be. The best gear you can get is Sacred legendary and Sacred unique—besides the ancestral items that can drop at world tier four, these are the most powerful available.