Mallon

Mallon was a member of the Gamma Hromi II Gatherer clan.

He was put in charge of the Gatherers by Brull while Brull was aboard the USS Enterprise-D to engage in peace talks with Acamarian sovereign Marouk and Gatherer leader Chorgan. (TNG: "The Vengeance Factor")

Mallon was played by an unknown actor.

According to the Star Trek: The Next Generation Companion, Mallon was played by Marina Sirtis' husband Michael Lamper. He actually played another unnamed Gatherer, however.