This is a Brute honour guard from Halo 2.Brutes are ape-like creatures who are very strong and berserk if they take too much damage.Originally Elites were the honour guards but since the killing of the prophet of  Regret the elites were considered unwealthy. After the Arbiter was asked to retrieve the index or "sacred icon" as the covenant called it the brutes started to murder the elites along with jackals and drones whereas the hunters and grunts allied with the elites and fought alongside.