No Stone Unturned Achievement in Halo: The Master Chief Collection

In total, there are 8 terminals spread across four specific missions within the Campaign that must be activated for this achievement. These terminal stations are well-hidden so it will take a keen eye and some exploration in order to track them down. You’ll know when you’ve found a terminal by the spotting a large cylindrical console-like structure that opens once you approach it.

When the terminal opens, it will reveal a large holographic sphere of blue and yellow light. Simply approach the holographic panel and hold the action button to activate it. From here, simply skim through the pages until you reach the final message. After sitting on this final page for a few seconds, the screen will turn red and the terminal will redirect you to another database full of information, where you will have to skim another set of two or three pages.

Take note that you do not necessarily need to read all second database of notes in the terminal because progress towards this achievement registers as soon as the terminal redirects you after the red screen. It is highly recommended to spend the time in reading the notes of each page though since they will provide subtle backstory to the Halo Universe. Once all 8 terminals have been activated, this achievement will unlock.