Nirncrux, commonly called red brittle, shake stone or miner's bane, is a red stone found only in Craglorn. In its raw form, it releases a poisonous gas when cracked which can cause symptoms ranging from nausea, body tremors, and disorientation to convulsions, slurred speech, memory loss and death. Ancient Nedes discovered how to use it to harness the power of the stars, and the Upper Craglorn storyline focuses on stopping the Scaled Court and the Iron Orcs from rediscovering these secrets.
As a reward for questing in Upper Craglorn, you can earn a piece of gear with the unique Nirnhoned trait. Once researched, Nirnhoned weapons and armor can be crafted using Potent Nirncrux or Fortified Nirncrux, respectively. These materials can rarely be obtained by harvesting any crafting node in Craglorn. They can also be obtained from Heavy Sacks in the region, or from killing creatures that drop medium armor clothing materials such as welwa. Nirncrux materials were originally limited to Upper Craglorn, but can now be found throughout the entire zone.
In addition to the crafting aspect, access to Stable Nirncrux can be earned by completing a group event at an Iron Orc Nirncrux Mine. Activating Stable Nirncrux will grant the Nirncrux Infusion Physical Resistance buff for 1 hour.