The Dragon Helmet is a mystical helmet that is part of the complete set of the Dragon Armor, which also includes the sword, shield armor piece. When united with the rest of the armor, it can control the Firstbourne. It was once worn by the First Spinjitzu Master, before he left the Realm of Oni and Dragons. It was located in Firstbourne's Nest, until it was found by the Iron Baron and Wu, and the latter now wears it.
When Iron Baron and Wu made it to the nest, he stole the armor and tried to control the Firstbourne. However, Wu told him it was not the armor that controls her, and she promptly buries him in molten rock. Wu then took possession of the Armor.
Wu wore the helmet with the rest of the Dragon Armor during his fight with Garmadon.