Mark of Shame
From Halopedia, the Halo wiki
The Mark of Shame is a tattoo-like mark given to those who have either disgraced or turned away from the Covenant. The Mark of Shame is imprinted permanently onto the bare chest of the being by means of branding heated metal.
After being branded with it, the being is executed soon thereafter out of sheer humility, perhaps harnessing the last bit of honored dignity they can draw up. The only known exception of this tradition was the Supreme Commander in charge of the protection of Installation 04. He became the Arbiter in order to settle the act of Heresy of Sesa 'Refumee on Threshold.
The Mark of Shame was likely adapted from Forerunner symbolize by the Covenant, since the Mark can be seen in the Halo 3 level The Covenant serving as the symbol of Installation 03.
Trivia
- The Mark of Shame is available as a Multiplayer Emblem in Halo 2 and Halo 3.
- If you look closely, the Mark of Shame can be seen on the Elites' armor on the Halo 3 Campaign, perhaps out of deference and respect for their current Arbiter.
- It also seems that the Arbiter's name means nothing and is not mentioned due to the disgrace signified by the mark.