DaiMon Tarr was the commander of a Ferengi D'Kora-class marauder responsible for the theft of a T-9 energy converter from an unmanned Federation outpost on Gamma Tauri IV, in 2364.

Tarr's starship was later pursued by the USS Enterprise-D in an attempt to recover the energy converter, it was finally able to confront the Marauder in the Delphi Ardu star system. Soon thereafter, both ships were incapacitated by an unknown energy beam from a nearby planet, later discovered to be a former outpost of the Tkon Empire. Tarr and Captain Jean-Luc Picard both agreed to send away teams to the planet in order to disable the energy beam.

His team attacked the Federation away team, and were stopped by the Portal, a guardian of the Tkon Empire. At first the Portal was going to destroy Tarr and his ship, but after listening to Commander William T. Riker who led the Federation away team, the Portal freed Tarr and his ship. Following this encounter Tarr agreed to return the stolen energy converter. (TNG: "The Last Outpost")

Tarr, played by actor Mike Gomez, was the first Ferengi seen in the Star Trek saga.
The script and Star Trek Encyclopedia (3rd ed., p. 491) spelled his name as "Taar", but the end credits of the episode spell it as "Tarr".
Tarr appears in the Menage a Troi second draft script where he fulfills the same role that DaiMon Tog does in the finished episode.