The Iron Crown is the royal crown of the king of Tashar.
The Iron Crown was created when the hobgoblin Kreggnar used wish magic to protect himself from the power of the Thranish wizards during Tashar's war to win independence from Thrane. Kreggnar may also have created the Lead Chest as part of this same wish, but that artefact was never as well-known. When a king of Tashar is crowned, he swears to do everything in his power to protect his subjects (on the condition that they remain loyal). Kahaeshan wore this crown almost constantly while impersonating Tazrak to protect his identity. The crown is now guarded by Hasarok.
This heavy spiked crown protects the wearer from divination and many other forms of magic. Tazrak described it as uncomfortable.