The Illuminated

The Illuminated are the guards of the City of Brass, consisting of approximately fifty thousand efreet. The standard uniform of an Illuminated includes long gray robes and a pendant worn around the neck that constantly churns with flame. Most Illuminated are armed with a scimitar. They are loyal to the Grand Sultan and take any threat towards him very seriously.

Encounters with Vox Machina
Vox Machina first encountered the Illuminated in at the gates of the City of Brass, where they had to barter with the efreet to gain entrance to the city.

The next time they had a direct encounter was in where, during the battle with Ghurrix, a single member of the Illuminated arrived at the fight scene, saw what was happening, and joined the battle himself, fighting against Vox Machina. After killing Ghurrix, Scanlan quickly used Modify Memory on the efreeti, convincing him that Ghurrix had been plotting to murder the Sultan, and that the efreeti had fought alongside Vox Machina. The efreeti believed him and, as more members of the Illuminated appeared on the scene, the first one told his modified tale to the others. His comrades didn't quite believe the story, but nevertheless felt Vox Machina was not a threat and left without any further conflict.

Trivia

 * Matthew Mercer has stated that, if not for Scanlan's clever use of Modify Memory, Vox Machina would have gone up against the entirety of the Illuminated guard force.