From Halopedia, the Halo wiki
Vidmaster Challenge A
Vidmaster Challenge A is an achievement in Halo: Spartan Strike. It is unlocked by completing Operation A, Mission 6 with the Blind and Thunderstorm skulls active. The achievement is worth 10 Gamerscore. It is represented by a circle with "A-6" and the Blind and Thunderstorm skulls inside it.