Terix
The Terix was a Romulan  warbird that was in service with the Romulan military in the late 24th century. Commanded by Commander Sirol, the Terix discovered a hull fragment from the Starfleet testbed vessel  in the Devolin system in 2370. The warbird was subsequently ordered to find the rest of the ship. When the  arrived with the same mission, Sirol claimed that the Terix was investigating gaseous anomalies.

After the Enterprise-D entered Gamma-601 to salvage the Pegasus, the Terix "accidentally" sealed the starship inside during some "geological experiments." The Terix offered to transport the crew of the Enterprise-D out, but the starship escaped on its own using the Pegasuss phasing cloaking device. ()

The Terix was Tomalak's flagship during a face-off in the Romulan Neutral Zone in an alternate 2370. ()

Background information 
According to the script for the episode "The Pegasus", the pronunciation for Terix was "TER-rix".  Later, for the episode "All Good Things...", the pronunciation was changed to "TAIR-ix". 

The  RPG sourcebook gives its registry as I.R.C. 1969.

One of the several D'deridex-class ships in Star Trek: Armada II was the Terix.

This starship also shares a name with the Terix system.

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Terix, IRW