Tyrava was an enormous starship built secretly during the 23rd century by the Romulan Ship-Clan of the same name, as a refuge for Romulans fleeing the rule of the Romulan Star Empire. She later played an essential role in the Romulan Civil War. (TOS - Rihannsu novel: The Empty Chair)
By the time of the Romulan Civil War, Tyrava was home to 380,000 people, gathered from remote colonies of the Empire including Gahvenn and Thalawir. Some had fled Imperial persecution, others from colonies that had been neglected by the government and were starving; all were said by Veilt tr'Tyrava, their captain and the chieftain-designate of Clan Tyrava, to be willing to risk death every day rather than remain under Imperial rule any longer.
Before the Battle of Artaleirh, Ael t'Rllaillieu secretly sent a message to Tyrava asking for their assistance. The ship arrived just in time to save the Free Rihannsu forces, and USS Enterprise and ChR Bloodwing, from an attack by Klingon ships. From then until the end of the war, Tyrava travelled as part of the Free Rihannsu fleet, taking part in the Battles of Augo and Eisn, and finally, and crucially, conveyed hundreds of thousands of troops to ch'Rihan itself, mostly members of her own crew. (TOS - Rihannsu novel: The Empty Chair)
Tyrava possessed three backswept cylindrical hulls mounted in parallel, at 120-degree angles, in a central framework. Each hull was over 3,000 meters long, yet Veilt tr'Tyrava implied that the other latter-day Clan-Ships were larger still. (TOS - Rihannsu novel: The Empty Chair)