So after many reports surfacing on the internet I decided to the test the theory that only 1 out of the 10 Majestic Map Pack Achievements for Halo 4 could be unlock through Custom Games instead of the usual DLC Matchmaking requirement.
Bird of Prey – 50 Gamerscore
In Majestic DLC matchmaking, perform 5 ‘airsassinations’.
Well, looks like there’s a glitch in the achievement matrix. No need for the blue or red pill. The Bird of Prey Achievement, which requires 5 air assassinations can be unlocked through Custom Games.
– Chief Landless