The Decius was a holographic Romulan D'deridex-class warbird. The starship hologram was created for a holoprogram of a fictional future by Barash for Commander William T. Riker in 2367.

In the program, that took place in 2383, the Decius transported Admiral Jean-Luc Picard, Deanna Troi, and Ambassador Tomalak to the USS Enterprise-D to conclude treaty negotiations for an alliance. (TNG: "Future Imperfect")

According to the Star Trek: The Next Generation Companion (2nd ed., p. 148), the Decius was named after the overzealous Romulan officer Decius seen in the Star Trek: The Original Series first season episode "Balance of Terror".
According to the script for this episode, the pronunciation for Decius was "DEE-see-us". [1]
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