From Halopedia, the Halo wiki
The Sangheili Ultra, also known as Evocatus (plural Evocati), is the highest regular rank among the Covenant's Sangheili warriors. While most Ultras are more warriors than leaders, specially appointed members of the class known as Evocati Delegatus take on a role analogous to high-ranking field officers.
Roles and responsibilities
Sangheili Ultras are extremely skilled veteran Sangheili warriors who have not pursued a career of leadership, instead focusing solely on combat; this is in contrast to the Majors or Obedientaries, who served as the Covenant's primary field officer class. The rank of Ultra was considered a great honor both among the Sangheili and within the former Covenant, which stored records of their exploits in the record vaults of High Charity. Not many Sangheili remain as Ultras for long; typically, such Sangheili are expected to ascend to posts such as that of a seneschal, enter a career in politics as a Councilor, or return to their ministry to serve as instructors. Ultras are sometimes deployed on high-priority missions often alone. While they most often engage in open battle, Ultras are known to command Protos-pattern Scarab assault platforms.
Ultras attached to Covenant armies rarely answered to their warhost's commander, but in practice, they were nevertheless expected to exhibit a certain degree of cooperation. To accomplish this, Ultras elected special representatives known as Delegatus from among their ranks, who would swear binding oaths to obey their warhost commander's orders until all of their objectives were completed. While these Ultra "officers" were not officially leaders within the Covenant chain of command, their expertise and authority was universally recognized among Covenant troops. This role is essentially analogous to UNSC Warrant Officers.
Following the end of the war and the collapse of the Covenant, many Sangheili continued to genocidally hunt down and slaughter the Jiralhanae. While the two species typically did not work together due to their feud, several Sangheili Ultras were recruited into the Banished as mercenaries by Chak 'Lok after he joined. They later fought in the Battle for Zeta Halo in 2560.
Ultras wear pearlescent armor with higher-than-average shield strength. They sometimes wear unique armor with red markings and a crested helmet similar to that of the Sangheili Councilors. Other Ultras may opt to wear (or are issued) a white version of the standard combat harness or Storm harness. War Games simulations of Ultras may have them depicted employing a maroon-coloured Warrior harness.
In combat Ultras typically wield Okarda'phaa-pattern plasma rifles, though they also commonly use plasma repeaters and concussion rifles. Ultras often use energy swords in close combat. War Games simulated Ultras are known to carry Scattershots and Gespu-pattern fuel rod guns.
Unlock: Achieve Warrant Officer.
Halo 5: Guardians
In Halo 5: Guardians, Elite Ultras spawn as a boss in the Warzone and Warzone Firefight gamemodes, clad in Warrior harnesses and wielding Scattershots or Fuel Rod Cannons. In basic Warzone, two Elite Ultras spawn on the map Raid on Apex 7. After 4 minutes pass, both are dropped off by Phantoms on opposite sides of the map, one at an outpost by the beach, and the other at the outpost past the rock bridge north of the Spire. Each is accompanied by a few Kig-Yar.
The Elite Ultras' shields are stronger than most Sangheilis', but they can be killed instantly from an assassination/beatdown or a vehicle splatter. They are armed with a fuel rod cannon and a scattershot, the only Covenant boss with Promethean weapons.
In Halo Infinite, Elite Ultras are combatants in the campaign. Their shields are significantly stronger than those of the lower ranking Mercenaries and Officers, and their combat harnesses are equipped with active camouflage. Ultras usually carry powerful weapons, such as Energy swords and Heatwaves, but are able to pick up other weapons and use them for their advantages. Ultras are encountered less often than Officers, but more frequently than Warlords in the campaign. Ultras typically guard key areas of Banished facilities or lead small groups of lesser Elites into combat.
List of appearances