If you are in the endgame of Diablo 4, then you will likely be looking for more advanced crafting materials. Whether you want to fully upgrade your gear using resources like Baleful Fragments or are trying to imprint certain Aspects onto your gear, the materials you need are far rarer in the endgame than they were during the main story.
Perhaps the most difficult material to acquire in the endgame of Diablo 4 is Sigil Powder.
Sigil Powder only has one use in Diablo 4, and that’s to create Nightmare Sigils. Nightmare Sigils are used to enter Nightmare Dungeons, which are harder and more rewarding forms of dungeons in Sanctuary. The higher-tier the Nightmare Sigil, the more Sigil Powder you need to craft it. You can craft Nightmare Sigils as well as salvage them at The Occultist, which is where you will also acquire Sigil Powder.
Getting Sigil Powder in Diablo 4
Currently, the only way to go about acquiring Sigil Powder is to Nightmare Sigils of any tier. This is the exact in-game description of Sigil Powder in Diablo 4.
In order to get your first Nightmare Sigil, you need to head to The Whispering Tree after beating the main story and World Tier 3 Capstone Dungeon in Diablo 4. Here, you can take on tasks to acquire Grim Favors. You need 10 to earn a random cache, which has a chance to contain a Nightmare Sigil. You need to keep doing this until you receive a Nightmare Sigil.
You can then use that Nightmare Sigil to enter a Nightmare Dungeon. Once inside the dungeon, Nightmare Sigils will drop as loot from random enemies and you will also receive them as a reward for completing the dungeon itself. Then, you will have enough Nightmare Sigils to start salvaging them in order to receive Sigil Powder. You can then use the Sigil Powder to make higher-tier Nightmare Sigils.
It’s somewhat of a complicated process, as you need to salvage a Nightmare Sigil in order to receive Sigil Powder, but then you use the Sigil Powder to craft Nightmare Sigils. Once you get into the flow of the endgame in Diablo 4, you will start to easily understand how the system works.