Scimitar class

The Scimitar-class warbird was a type of dreadnought that saw service in various Romulan factions during the late 24th and early 25th centuries. (Star Trek Nemesis, Star Trek Online)

History
During the late 24th century, the prototype of the class, the IRW Scimitar was built in secret to counteract the Dominion threat. With the end of hostilities between the Romulan Star Empire and the Dominion in 2375, demand for the new class of dreadnought slowed. Only the prototype was completed. In 2379, Shinzon and his Reman forces seized the Scimitar and used it to destroy the other uncompleted Scimitar-class ships, so no one could use them against him. (TOS novel: Captain's Blood)

Later that year, the original Scimitar was lost in the Battle of the Bassen Rift. (Star Trek Nemesis)

The design of the warship, however, was recovered and new vessels based on the Scimitar 's design were built by both the Tal Shiar and the Romulan Republic. By 2409, the Reman Resistance had acquired Scimitar-class ships as well. Additionally, at least one Scimitar-class ship had been assimilated by the Borg. (Star Trek Online)

Technical Data
Like the original prototype, all Scimitar-class warbirds were massive ships that were very heavily armed, even for ships of their size. Scimitar-class vessels retained elements of the prototype Scimitar 's advanced cloak and could fire and use their primary and secondary shields while cloaked. Many even retained the thalaron weapon, capable of wiping out all life in a broad area in front of the ship.

At least three variants of the Scimitar-class were fielded by the Romulan Republic, each with a slightly different hull design and capabilities. These variants were the Scimitar-type (which looked exactly like the original prototype), the Falchion-type (which appeared very similar, but with a green deflector on the nose and bussard collectors on the nacelles), and the Tulwar-type (which had a more open hull structure and more compact wings).

However, unlike the original prototype, many of the Scimitar-class ships suffered from various limitations. Firing while cloaked severely drained their weapons systems and could only be maintained for brief periods of time. The thalaron weapon, if equipped, could only be fired while decloaked and severely limited the ship's mobility while deployed. Additionally the cloaks used on these vessels, while still very advanced, were no longer impenetrable. (Star Trek Online)


 * While various in-universe explanations related to the loss of the original prototype or changes in technology since 2379 may be used to explain the lesser capabilities of the Scimitar-class as compared to the original Scimitar, in reality the changes were introduced to balance game-play.

Star Trek Online: Valkyries/Star Trek: Justice continuity
In 2412, the Romulan Republic sent a Scimitar-class warbird, the RRW T'Rul, to serve as their flagship during the Borg invasion of the quadrant. Under the command of Admiral Sellis, the T'Rul fought alongside the Federation fleet in the Second Battle of Wolf 359. The dreadnought was disabled during the course of the battle, but was later repaired.

The T'Rul was noted as being marginally less heavily armed than the original Scimitar, having only 42 disruptor banks and 23 torpedo launchers. Previous to its appearance in command of the Romulan Republic fleet over Earth, Starfleet was unaware that the Republic possessed Scimitar-class ships. (Star Trek: Justice: "Vengeance")