From Halopedia, the Halo wiki

The QezoY'asabu (English: Obsidian Wing) was an ancient model of the Banshee that was built primarily for stealth operations. The craft featured active camouflage systems and refined sensor bafflers. The QezoY'asabu was deployed by Covenant Special Operations units for inquisitorial operations. The QezoY'asabu was known only to the Office of Naval Intelligence through the analysis of Covenant operational records.[1]