What magic item does Hades have what are its powers in chapter 13 of the Lightning thief?

In Chapter 13 of "The Lightning Thief," Hades possesses the Helm of Darkness, a powerful magic item that grants him the ability to become invisible. This helm allows Hades to move unseen and undetected, enhancing his already formidable presence as the god of the Underworld. Additionally, it symbolizes his control over the dead and his dominion over the shadows. The Helm plays a crucial role in the conflict between the characters as they navigate their challenges.