|20||5789 XP, $86, Rocket Launcher or Shield|
You need all of the help you can get and Roland decides to call in a favor with someone called the Slab King. He gives you a note to deliver to him, so once you grab it, you'll need to get to Thousand Cuts, which is accessible from The Highlands. This entire area is inhabited by bandits, so you should have no trouble dealing with them, as you will know what to expect.
There will be Marauders, Psychos, Bruisers and Goliaths to contend with, as well as some Buzzards flying around to annoy you. Some of the Goliaths will be Caustic Goliaths, meaning that corrosive damage won't work on them. You'll eventually reach the front door, which doesn't open, so take the stairs and drop inside to begin the real initiation.
To impress the Slab King, you're going to need to fight off a lot of bandits, which include all of the above. Some of them will be Badasses, like the two Goliaths that are by his side. Once you've killed everyone, the Slab King congratulates you and reveals that he is really Brick, another of the first game's playable characters.
Hand him the letter and Jack will chime in, saying he's about to begin a mortar assault on the area. Wait for Brick to open the door and then follow him through the area, killing Loaders and dodging the mortar shots, which are designed with red circles on the ground. You are targeting the beacons, which are surrounded by a reflective shield. Wait for Brick to destroy the shield, then shoot the beacon to destroy it. Do this for all three, then return to Sanctuary to turn in the mission.
Got The Band Back Together
Completed the mission "The Once and Future Slab"