From Halopedia, the Halo wiki
Blademaster is a title used by Sangheili to indicate a Sangheili-ai, a master swordsman. The "-ai" suffix is applied to the surnames of blademasters, an honorific bestowed upon the Sangheili in a ceremony after they choose to dedicate their life to the perfection of their swordsmanship. Blademasters are entitled to wear gilded armor, denoting their master rank.
Toha 'Sumai was one of the preeminent swordfighters of his time, though the aristocratic 'Sumai clan appears to bear the "-ai" suffix in perpetuity; the family's keep and all known members of the clan both hold the honorific. Vul 'Soran, the second-in-command aboard the CAS-class assault carrier Shadow of Intent, is a blademaster, though he lacks the "-ai" suffix. Okro 'Vagaduun of the Banished is another blademaster who lacks this honorific suffix. Other notable blademasters include Tel 'Szatulai, Bero 'Kusovai, Tulum 'Juranai, Inslaan 'Gadogai, and Jega 'Rdomnai of the Hand of Atriox.
List of appearances