The Demon Crucible is crafted in the Hellfire Forge. Its main use is to release Will into the Aura. Each chunk has an Aura and each chunk holds up to 100 Will. The only initial way to fill up the Aura is via the Demon Crucible.
Once you have put down your Crucibles you will need to place a Tartaric gem into the Crucible by right-clicking the Crucible with the gem in hand. This gem should have at least 100 Will in it. Slowly but surely the Gem will empty into the Aura.
It’s a good idea to show chunk boundaries (F3 + G) that way you can set a Crucible in each chunk.