Invincibility
From Halopedia, the Halo wiki
Invincibility is a piece of equipment featured in Halo 3.
It confers the user with a brief period of invulnerability. When activated the player is covered in shining bands. It is known to be possessed by some or all Brute Chieftains in Halo 3, giving chieftains a brief period of time where they may chase after the player with the Gravity Hammer unhindered, giving them a significant tactical advantage. In campaign, it can be found on some dead Brute chieftains that haven't used a powerup yet.
It has a similar appearance to the Cloaking equipment, except that it glows a gold color, rather than a cool blue color.
It is not present in multiplayer.
File:Invincibility 2.jpg
The power up is never found on it's own, and can only be taken from the dead bodies of Chieftains who have not used it, except on the last level of Halo 3.
