To unlock the Terminus Achievement, you must find all seven terminals throughout the game. Here’s where you can find all seven:
In Chapter 2: Requiem, you will reach a large tower near the end of the mission. Before attempting to go up it, kill the armored Hunters, and look for a main ramp leading up to the central tower’s elevator shaft. Search underneath the transparent ramp to find the first terminal.
In Chapter 3: Forerunner, after Master Chief’s screen flickers while searching for the first of two objective at the beginning of the mission, Cortana will say “What’s that distortion?” The terminal will be directly ahead, on the ground floor of the central Promethean building, below a circular structure with three columns.
In Chapter 4: Infinity, after meeting up with the UNSC allied soldiers, there will be a cutscene. Once the cutscene ends, turn around to find the terminal.
In Chapter 5: Reclaimer, after getting Cortana back, you will be instructed to escape using an elevator. Before using the elevator, go down the hall to your right, as you enter the hall leading to the elevator, to find the terminal.
In Chapter 6: Shutdown, you will fly a Pelican to multiple locations. Once you reach the Production Tower (which is the third tower), Cortana will say you have to locate the control room. Take the gravity elevator up, then cross the energy bridges toward the objective. Once you reach two Hunters, go back across the energy bridge you just crossed, and go to the right to reach a new platform. The terminal is on the backside of the isolated platform.
In Chapter 7: Composer, after killing the two Hunters, there will eventually be a long cutscene with the Dr. Tillson. Once the cutscene ends, look directly ahead for a building with “ATRIUM” written on it. Look below that building, inside a small cave formed by rocks, to find the terminal.
In Chapter 8: Midnight, after crash landing on the enemy ship, you will have to fight Protheans through several chambers. After entering the third room, look behind the central pillar to find the terminal.
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