Hey there not sure if you all know about these or have found anymore. The one I have found is for Specter only and it is in the room where you look at the monitor and see Nicholai shooting his squad and locking the door on him. There is a computer terminal in there its a generic green display monitor like the millions of other but if you go up to it you can interact with it. If your not specter is just say's this challenge mission is for spectre only. I haven't had the time to go back there and try using the terminal with specter to see what it does but am wondering if anyone else has noticed or found similar things that allow you to interact with specific characters to open up side-missions or quests or whatever if someone does go try this with specter post what happens as I will be trying it when I get some free time. Hope we can figure out this mystery together, cheers!