Entropy : Zero

Earned during chapter 3 Low

you will be in a subway station full of zombies this is the first area where you can start lighting 20 zombies up with road flairs . Kill all the zombies and head up the stairs into the room where you have to flip the switch to open the door. Ones you enter do a 360 and look at the door you just came in brack the 2 boxes next to the door and you will find a Half Life 3 reference on the wall.

https://steamuserimages-a.akamaihd.net/ugc/87637819981412289...