The Sangheili Prime is a Sangheili title or rank which appears in Warzone simulations as a boss.
Ossoona - Halopedia, the Halo wiki
halo.wiki.gallery/images/thumb/6/63/Enc22-Sangheil
In Halo, why did the Grunts side with the Brutes instead of the Elites? - Quora
Sangheili, VS Battles Wiki
Sangheili Field Marshal - Halopedia, the Halo wiki
Just found out about Bungie's EARLY Promethean knight-esque concept art : r/ halo
Sangheili Minor - Halopedia, the Halo wiki
Sangheili, HaloHistory and Gaming! Wiki
Field Master - Halopedia, the Halo wiki