Belly of The Beast: Darkest Before Dawn
Run to the left, over the pathway. Pick up the ammo and continue your advancement until you reach a sealed door with Gears symbol on it. Here you can pick up both the grenades and a twenty-second COG Tag. Now move back a bit and take the path down from the crossroads.
Deal with a group of annoying Lambent Wretches. Pick up the ammunition in a cave to the left and continue onwards. Fight off another group of the exploding crawlers. After the falling down, take more ammo if you need it. A group of Drones will engage you - I believe it's a nice refreshment after the streams of volatile Wretches. After your inevitable victory, pick up the twenty-third COG Tag near the base of the ladder.You can get up the ladder and kick open the door if you need ammo or grenades.
Continue on your path. A lone Locust will start shooting at you; you can shoot the column at his side to cause a rock slide as an answer. After some more running, rocks falling and Lambent Wretches exploding,you will eventually meet up with a Boomer. If you need to get closer, run from cover to cover and deal wit the brute at your optimum range.
Turn left, pick up ammo and continue running downwards. After another rapid descent, you can get more ammo if there is any need. I suggest defeating Lambent Wretches first. Soon you will come to a point where your path splits in two. Again, no need for a separate
walkthrough here, as both paths are essentially the same: Run forward, deal with the attacking Locust, and pick up the ammo. If your friend needs help, shoot the enemies on his side as well. Keep an eye out for each other's situation, and everything will be OK.
After you meet up, take the path down for the ammunition and grenades, then get back up and take the turn to the left. The tunnel is full of both cover and enemies, so fight your way through like a true Gear should. Soon you'll reach a clearing. An ammo box can be found to the left. Near it, behind a rock wall, you can find the twenty-fourth COG Tag. After that, continue moving forward, and the chapter will end.