Red Faction

Missable.

This is in the Underwater Research area, after you take the submarine from the Geothermal Plant. The trophy will start when a fellow miner gives you a suit and takes all your weapons bar a silenced pistol. You will have to get through three areas without triggering an alarm to reach Gryphon and get the trophy. You can kill guards and civilians while doing this, just as long as no one activates an alarm. You can do this on any difficulty but on higher difficulties the guards will detect you from a greater distance so the path may vary slightly. I recommend saving often so that you don't have to redo the whole sequence if you mess up.

Do the following to get through it safely:

1. From the miner, holster your pistol and head upstairs into the office area. Head up the stairs immediately in front of you and head to the end of the corridor, hiding in one of the offices to let the guard pass.
2. Once at the end of the corridor, head down the staircase and into the door to the left as you come off the staircase. Walk to the elevator at the back of this room while keeping your distance from the guards.
3. In the next area, ignore Hendrix and head upstairs. Go past the guard when he's not right in front of you, down the stairs and straight to the elevator.
4. When in the Executive Suites, you want to keep a wide berth as the elite guards can detect you from easier than standard guards. Head up the stairs to your left and enter the first door into the Security Room when no one is looking. Kill the guard at the monitors, then shoot all the monitors twice to destroy them as this will disable the cameras.
5. Move the body out of sight, then leave the Security Room and continue forward until you reach two offices. The office on the right contains Gryphon. Head straight into him and it will trigger a cutscene, unlocking this trophy.

The following video demonstrates both this trophy and Situation Normal immediately after. I do it on Impossible difficulty so the path I take will work on any difficulty.