Lights of Sanghelios

Honor Guard Ultra is a Covenant Sangheili (Elite) rank. This rank commands the 'lower' Honor Guard Elites of the High Prophets. It is equal to the rank of Honor Guard Captain of the Brute Honor Guard.

They are likely more skilled than their subordinates, with years of experience in the Covenant Honor Guard, which is particularly impressive considering the prodigious combat abilities of any in the Honor Guard.

Appearance
These Honor Guard Elites sport the same ornate armor as the rest of the Honor Guard, with the exception that the under armor they wear is white instead of crimson. This color is consistent with the Ultra Elites of the regular Covenant army, hence their title.

Combat
Honor Guard Ultras have never been directly seen in combat. Many players believe that one appears at the end of the level Gravemind but this Elite is actually the glitch known as the Honor Guard Councillor.

Five Honor Guard Ultras are seen in the cinematic of Sacred Icon (Level) when they, along with regular Honor Guard Elites, are stripped of their position, giving it up for the new Honor Guard Brutes and their Honor Guard Captains. One is seen giving his helmet to another Brute.

In addition, three Honor Guard Ultras are seen killed fighting the Brutes around the middle of the level Gravemind (Level). They wear Honor Guard armor but without helmets, as they no longer held that position when they were killed.

It is theorized that Honor Guard Ultras are more likely to withstand the Brute onslaught than regular Honor Guards, due to their superior shielding and years of combat experience.

Trivia
There are corpses of them scattered throughout Gravemind with Energy Swords and they are seen in Halo 2 cutscenes, but you do not seem to combat against a Honor Guard Ultra at all in Halo 2, with the exception of the glitch at the end of the level, Gravemind.