How to Unlock 'Abyss Conqueror'

Rescuing Charles: Inspect the files on the whiteboard to find 'The End (5/8) - Robot Puppets'. Interact with the large life support device and then the computer. Read all files on the PC desktop, especially the diagram on the far right. Return to the far left of the lab and interact with the chain console control panel. Adjust the coloured lamps to match the computer diagram: press the purple/orange button twice, the yellow/green button once, and the blue button twice. This will reveal stairs leading down. Enter the Secret Corridor, examine the courier clothes if desired, then enter the doorway at the far left. In the secret room, examine the diary and then the Beta Type Consciousness Transmission Device to find 'The End (6/8) - The Research Information of Consciousness Transmission Device'. Speak with Charles, then grab the Crowbar from the far right of the room. Use the Crowbar on the holding cell door to free Charles and unlock the 'The Story of Rescuing the White Mustache' Trophy/Achievement.

Decision Time: You will be presented with two questions. The first answer has no impact. The second choice determines which of two Achievements you unlock: 'The Liberation' (by choosing to 'Turn off the equipment') or 'The Benevolence' (by choosing to 'Leave the equipment on'). Choosing to turn off the equipment also unlocks 'The End (7/8) - The History Between Edward and Luna'. You cannot unlock both Achievements in a single playthrough without reloading a save.

The Final Confrontation: Regardless of your choice, you will need to return to the secret room where Charles was rescued. Head down the stairs when ready.