Steal the Baron's banner at the top of the ruined tower and bring it back to me. Then, maybe we'll talk.”— Torn, Jak II
The Baron's banner was an apparent territorial flag located atop an old ruined tower in Dead Town. When seen in Jak II, it was a maroon flag with a black logo planted on it the side closest to the pole which held it. It was used as a mission objective early on in Jak II in the mission "Retrieve banner from Dead Town", given by Torn as an initiation to Jak and Daxter for membership in the Underground.
The logo is not seen again in the series, making it unclear whether or not it is actually Baron Praxis' personal banner or just planted there as a test for new Underground members. The flag was technically a swallowtail pennant, which is typically used as a personal ensign of a military figure.