Tarr's starship was later pursued by the USS Enterprise-D in an attempt to recover the energy converter and was eventually confronted by the Enterprise 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.
Tarr's team attacked the Federation away team, and were stopped by the Portal, a guardian of the Tkon Empire. At first, the Portal was about 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")
The script for "The Last Outpost", as well as contemporary production art spelled his name as "Taar", as does the Star Trek Encyclopedia (3rd ed., p. 491) and StarTrek.com. However, the end credits of the episode spell the name as "Tarr".
According to the examples given in Mike Okuda's TNG Season 1 concept art for Ferengi ranks (also shown in the link above), Taar's tattoo, with two chevrons, indicated that he was a "salesman, second class". (Star Trek: The Next Generation - The Continuing Mission, p. 62)