The Relics of the Gree event will take place sporadically on the endgame planet of Ilum. It's there that a giant Gree starship will be discovered, explored, and possibly conquered. BioWare says that players can "earn exclusive Gree technology" in the form of cool new gear.
The galactic reputation system might be a powerful incentive to level up all over again. The system adds to the game a new rep grind, which can be leveled up by doing Gree, Voss, or military missions. Reputation points are shared across all characters and count toward the titles and rewards from reaching higher ranks.