Whispers Across the Galaxy Achievement in Halo: The Master Chief Collection

After reading all of the main seven terminals throughout the game (barring Cortana's terminal on "Cortana") and unlocking their corresponding achievements, load up "Halo" on the Legendary difficulty setting and return to the hidden room inside the cliffside cave that houses the seventh terminal.

Once inside, activate the terminal as you normally would and wait on the final page until the screen turns red. After this happens, the terminal would usually bring you further into the database for more information. This time, a direct message from Mendicant Bias, a Forerunner AI, will appear, stating the following: "You don't know the contortions I had to go through to follow you here, Reclaimer. I know what you're here for. What position do I take? Will I follow one betrayal with another?" After a few seconds of viewing this message, the achievement will finally unlock.