From Halopedia, the Halo wiki
Terminus is an achievement in Halo 4 and Halo: The Master Chief Collection. It is awarded for finding all the terminals in the Halo 4 campaign. The achievement is worth 50 Gamerscore in the original game and is represented by a symbol similar to the Didact's. In The Master Chief Collection it is worth only 20 Gamerscore and is represented concept art of a Forerunner monitor or ancilla.