Mark of Disobedience
From Halopedia, the Halo wiki
The Mark of Disobedience is a mark given to those who have disobeyed an order given to them by a higher-ranking individual. It is created by branding one's arms in a criss-crossing pattern using an Energy Sword. The only individual who is specifically known to have received the Mark of Disobedience is the Sangheili Zealot Saal, who was commanded to mark himself by Thel 'Vadam after disobeying an order not to torture the Kig-yar Reth.
It may be possible for a Sangheili to recover his honor after receiving this mark. When Thel explains the Mark of Disobedience, he states that "we will destroy the body so that his [Saal's] lineage will not suffer. If he performs well in battle". It is unclear whether all those who receive the Mark are allowed this chance, as Thel mentions that he needs all of his fighters and that Saal "can kill himself later", suggesting Thel might have given Saal the opportunity only because he needed him at the time.
List of appearances