The Fenix Rising Add-on for Gears of War 3 has 6 achievements worth 175 gamerscore.
Achieve level 100 a second time and choose to re-up for another tour.
Complete all 12 waves of Beast on all Fenix Rising maps.
Complete all 50 waves of Horde on any of the Fenix Rising maps.
Win a Versus multiplayer match as a team of five Recruit Claytons (any mode).
Win a Versus multiplayer match as a team of five Savage Marauders (any mode).
Achieve level 100 and choose to re-up for another tour of duty.