- “With this sacrament of blood, we journey into the Divine Beyond.”— Sangheili Field Marshal's mantra
Field Marshals technically are not a part of the Covenant's conventional forces, but instead a subset of the Zealot class of infantry. These Sangheili are charged with the recovery of Forerunner relics and the coercion of species who refuse to submit to the Covenant. Field Marshals' orders supersede all others and they report directly to the fleet's Supreme Commander. Besides leading large-scale ground operations, Field Marshals are known to lead small strike teams comprised of Zealot officers for operations that require both skill and precision to take out key targets to turn the tide of the war/make a key difference.
Its first encounter is in the level Winter Contingency when Noble Team investigate the Visegrád Relay. The Field Marshal jumps out of the shadows, with two Zealots assisting it, and attacks Noble Team; but its shields collapse due to gunfire and it escapes, the Zealots stay behind and are killed by Noble 5 and 6.
It later appears again in the level New Alexandria when the Covenant attack the building Noble Team are in. The Field Marshal appears in a Phantom and kills Catherine-B320 with a Needle Rifle as she was running towards the bunker entrance, which causes SPARTAN-B312 to take Catherine-B320's pistol and fire it at the Field Marshal with the rest of Noble Team firing at it as well, but the Field Marshal then orders the Phantom to retreat and escapes again.
Its final appearance is in the level The Pillar of Autumn when SPARTAN-B312 and Emile-A239 try to get to the UNSC Pillar of Autumn with The Package. The Field Marshal appears at the end of the level leading a squad of Zealots, and some Unggoy, who kill Emile-A239, forcing SPARTAN-B312 to fight his way to and take control of the mass driver. After SPARTAN-B312 kills the last two Zealots and the Unggoy, he/she then finally confronts the Field Marshal who is equipped with a Fuel Rod Gun and an Energy Sword. After an intense fight the Field Marshal is eventually killed by SPARTAN-B312.
The Sangheili Field Marshal's armor design is similar to that of most other Sangheili warriors during the Fall of Reach. For example, the Marshal's armor is appears to be a combination of a Zealot and a General in terms of aesthetics and overall design. The helmet is nearly identical to the Zealot helmet, save for two spike-like protrusions at the top of the helmet. The core body piece of the armor is identical to the Zealot armor. The shoulder pauldrons are almost identical in structure and shape as the General's, although the ornamentation is blue rather than yellow. Essentially, as with all other Sangheili warriors' appearances during the Fall of Reach, the Field Marshal's armor has tones and hues of dark violets and blues. The armor is an affirmative appearance of Covenant construction. Overall, the Field Marshal's battle attire is less ceremonious and designed for optimum efficiency in battle, while still emulating the traditionally sleek battle armor worn by the Sangheili throughout the Ages.
- In Halo: Reach, the Field Marshal and Zealots are the only Sangheili classes which cannot be fought in Firefight.
- The armor of a Sangheili Field Marshal is available as an armor permutation for Sangheili players who have reached the rank of Lt. Colonel in Halo: Reach. It is the last armor permutation a Sangheili character can receive.
- After its shields are depleted, the Field Marshal will switch from his Fuel Rod Gun to an Energy Sword if the player gets too close.
- A commonly used way to kill the Field Marshal on Legendary is to, after the Zealots are killed, use an overcharged plasma pistol shot then switch to a shotgun. With the shotgun, shoot then melee until you down the Field Marshal.
- Halo: Reach (First appearance)