Styx: Shards of Darkness

To unlock this Insignia, you must complete every zone in a mission without raising any alerts. An alert is whenever any enemy has a red detection meter above their head. For reference, here are the detection levels:

• Yellow - The enemy is suspicious and will look around (but not deviate from their path).
• Orange - The enemy is very suspicious and will investigate (walk to) whatever alerted them.
• Red - You're busted.

Make liberal use of your ability to Quick Save whenever you wish so that you can reload if you do happen to alert an enemy. Do not forget that you have invisibility for the tough spots! If your clone is detected it does not count against you. The red detection of bugs or boss fights does not count against you either.

The pause menu will tell you at any time how you are progressing with this insignia. You begin every mission with it satisfied and it will instantly update if you are spotted so check it before every Quick Save to ensure you're still undetected. This will unlock during the mission completion screen.

See Oh My Gob! for videos of a stealth run through every mission.