The Arbiter Eye Glitch is a that occurs during Halo 3's Campaign. The graphical error, which causes one of the Thel 'Vadam's eyes to turn completely transparent, occurs after cutscenes in various levels, which include Sierra 117, Crow's Nest, and The Covenant.
At the very beginning of the level, Crow's Nest, stand on the Arbiter's left and look at his head. His left eye will disappear and reappear numerous times. You can see straight through his head when it disappears.
This happens to both of his eyes, but never at the same time. He will still behave as if he's looking at you with both eyes. Also, his eyes are meant to be orange with black slits instead of pure black.
This also happens at:
- Near the end of Sierra 117.
- The Covenant, shortly after the cutscene where the Thel 'Vadam kills the Prophet of Truth.