This mission is started in Sanctuary when you talk to Sir Hammerlock after "Bright Lights, Flying City". The mission takes place in the Caustic Caverns and involves collecting audio logs about the origin of the Crystalisk and how it came to be violent.
- XP: 2333
- Money: 4 Eridium
- Gear: N/A
The first audio log is not far into the cavern. You'll enter an area with a bunch of Larval Varkids and a large yellow Dahl dump truck. Take a right and as you follow the path, there will be a trash pile on the right with the first log.
Continue along this path and kill the Crystalisks along the way. You need to kill five of them total for an optional objective. The path will lead through a small cave and come out at an outpost. Just outside the walls of the outpost, you will be attacked by Threshers. These should just be Tadpole Threshers and shouldn't be too much of a problem after handling the Gluttonous Thresher in "Bright Lights, Flying City". Make sure you kill five of them before continuing.
Once inside the installation, you'll be attacked by more Threshers but there will be some tougher Threshers in the mix including a Wormhole Thresher who will try to suck you closer to it so that it can stab you with the spikes on its body. As soon as you see one, make sure you kill it because aside from the obvious combat danger, it will also prevent you from being able to escape.
From the base, turn right and you'll see a set of large double doors that are stuck open. Go through them to enter a warehouse. The second audio log will be stuck to one of the pillars in the middle of the room. There are going to be a bunch of Larval Varkids in this room with a few Adult Varkids as well. Be careful with the Larval Varkids because they are also capable of mutating. With the number of them in the room, you could end up at a serious disadvantage.
Go through the double doors on the other side and you'll see more pools of acid. Further ahead will be a house filled with ammo crates. Fill up on whatever you need and go out of the back of the building. You'll come to the edge of a cliff. At the bottom of the cliff will be a third Audio Log. Collect this log and then climb back up to the top.
You'll notice there is a set of train tracks that run along here but the lead to a locked door. There is a small section of tracks between two large locked doors and on a pole nearby will be an ECHO device that starts the mission "Minecart Mischief". You don't have to do it now but I do recommend it because it will unlock a number of doors in the area for easier travel.
From where you found the ECHO device that started the Minecart Mischief mission, head southward and you'll start to see large round nests. You'll enter the Nether Hive. You'll encounter mostly Spiderants in this area but you may also bump into Threshers from time to time. Make sure that you kill at least 10 of the Spiderants here and then make your way over to the waypoint. This will lead you indoors. Inside, collect the last audio log and climb up the nearby ladder. Outside, there will be a large set of doors. Open them by using the valve and you'll be back at the beginning. Return to Sir Hammerlock for your reward.