Rocks D. Xebec

Rocks is a person or a group of people who were prominent 40 years ago, before the Pirate King Gol D. Roger came into power.

Overview
Not much is known about Rocks, especially among those who grew up after their time. They seem to have been powerful, given their prominence prior to Roger's time and the fact that Garp could not imagine what the Marines would do if they came back into power. Garp is connected to them in some way, with Hina suggesting that he got the distinction of "Hero of the Marines" from dealing with them.

Past
More than 40 years ago, Rocks was extremely prominent and defined an era that lasted until Gol D. Roger's rise to prominence as the Pirate King.

Reverie Arc
While Rocks had since faded out of the public eye after their era, Hina knew that they were growing in power even after losing their leader sometime in the past.