The Grey Mountains (Q."Oromistar", Ad."Urîd- Mizim") were a vast north-south mountain chain in southern Middle-Earth. The Grey Mountains are believed to have collapsed either with the Drowning of Beleriand in the First Age or with the great cataclysm that followed the drowning of Númenór in the Second Age. The northernmost remnant of these mountains was doubtless the North Reef, while furfher south the Hills of Bellakar and the Briy-Miyeséc in the Rây were believed to be remnants of this ancient mountain range as well as the westernmost arm of the Tûr Betark.