Alien Breed 3: Descent

Each single player level has a 'secret' collectible in them. They are represented by a floating blue Intex hologram. As with the Logs, you can get these across multiple playthroughs. You cannot rely on Free Play to get any you missed as you cannot save it. If you are only missing one “secret’ though, you can use Free play to collect the one you’re missing and the trophy will unlock just fine.

Locations are as follows:

Level 1 - Subversion
 
After going up an elevator after destroying the Gyro, you'll reach a hallway where a pressure leak prevents you from progressing and you'll be told to contain it using a valve. The room beside the valve will have a human corpse for you to loot and a Hardened Armor inside. Turn the valve, which will result in an explosion. You'll then have to escape this hallway onto the other side to safety. As you're making your way down, when you enter the second open area, a cutscene will initiate in which a piece of a wall gets torn down, allowing you passage into the room next to it. The first 'secret' collectible is inside this room.

Credits goes to TheDuckofDK of YouTube

Level 2 - Re-entry
 
Not too far off in the beginning of the level, you'll enter a room with two electric circuits jolting above you, which in order to proceed you have to turn off the Air Vents and be forced into a 1 minute survival battle. After the countdown, exit this place by walking across the now lowered fans and instead of going to the right, go left into some ventilation tunnels where you can see further down some fire tanks you can blow up with your Blaster. Traverse back to the room with the electric circuits and you can now go through the newly opened entryway. The second 'secret' in the game is just down this tunnel.

Credits goes to TheDuckofDK of YouTube

 

Level 3 - Determination
 
Near the end of the level, a countdown will initiate in which you'll only have 10 mins to make it to the exit elevator. When you finally get to the elevator and instead of going in it, go pass it and onto a walkway in which you'll see some fire canisters than you can "Dislodge". Dislodge them and go back to where they landed. Blow the canisters up, pick up the Storage Room Key-Card, and use it on the panel in this same room to unlock the door and grab the 'secret'.

Credits goes to TheDuckofDK of YouTube

Level 4 - Vengeance
 
In the mid-way point of this elevator, you'll reach an Override Console next to a Key Card Panel. To get to the 'secret', you must activate the Override Console, in which you'll have 5-6 seconds to reach the locked door on your right. It might take a few tries, but once you make it, the secret along with a few loot can be found inside.

Credits goes to TheDuckofDK of YouTube

Level 5 - Resolution

After dealing with the Part I in the Alien Queen battle, you have the option in going left or right, with right directing you to the next objective. Go to the left instead, and you'll find a platform you can ride up to a walkway above. The final 'secret' is located here.