The Grand Proxy was a high-ranking official of the Ferengi Alliance, and was appointed by the Grand Nagus to act as his representative in matters which he did not wish to deal with personally.
The Grand Proxy carried a staff as a symbol of the authority granted to him by the Grand Nagus.
In 2373, Neelix masqueraded as the Grand Proxy in order to convince Arridor and Kol to relinquish their hold on Takar, where they had been exploiting the Takarian populace using the myth of the Holy Sages. The plan fell apart when Arridor and Kol tried to kill the Grand Proxy, as per the rule that Arridor invented ("When the messenger comes to appropriate your profits, kill the messenger"). They hoped to continue their operations without interference from the Ferengi Alliance. Neelix's true identity as a member of the USS Voyager crew was subsequently exposed.
The commentaries and opinions of the Rules of Acquisition had sections regarding the Grand Proxy, including "Grand Proxy, avoidance of" and "Grand Proxy, censure by." The section titled "Grand Proxy, encounters with" advised readers to "see Hopeless Situation." (VOY: "False Profits")