The mogai was a type of large flying predator which were native to Romulus.
They have been known to fly near the firefalls on Romulus, as well as being spotted hovering in the skies above Ki Baratan. (TOS - Vulcan's Soul novel: Epiphany; TTN novel: Taking Wing)
In the 2370s, a new type of warbird entered service in the Imperial Romulan Fleet, and was named the Mogai-class after the creatures. (TTN novel: Taking Wing)