After we finish A Train to Catch story mission, we can go back to Sanctuary and consult the bounty board there, to find out that a new mission is available to us; a mission named Borderlands 2 The Good the Bad and the Mordecai.
In Borderlands 2 The Good the Bad and the Mordecai mission, Mordecai will contact us to say that he won two prizes in Moxxis Underdome (a location from Mad Moxxi’s Underdome Riot, the 2nd DLC of the first Borderlands game); and one of them is a treasure that was stolen by a thief known as Carson.
He wants us to travel to The Dust, and if we can find the treasure chest its all ours.
Years ago, Mordecai won the grand prize at Moxxis Underdome. A little while after that, a thief named Carson stole the loot chest and hid it somewhere in The Dust. Mordecai has informed you that, if you are able to find Carson and figure out where the guns are buried, you can keep them.
Item: Eridian Relic
Experience: 1820 XP
Upon arriving in The Dust area, we must get ourselves a vehicle and then go and jump inside the marked enemy base using the large angled rock (the same base from Too Close For Missiles optional mission).
Inside the base, we have to find Carson, but the only thing we discover is an ECHO next to Carsons brothers dead body, and by listening to it we learn that Carson was taken by an engineer called Gettle to the Hyperion Friendship Gulag.
In Friendship Gulag, the enemy forces are mostly comprised of human engineers and robot loaders, so assuming we have the proper equipment, the fight should not be as hard as the last time we visited this area (during A Dam Fine Rescue story mission).
The enemies will continue to spawn until we arrive at our destination, therefore we kill them however we feel its necessary. We cannot actually break out Carson, since hes dead, and the only thing to do here is to open the cells bars and pick up his ECHO recorder. We find out that another bandit called Mobley is now after the stash.
Next, we exit the Friendship Gulag and go back to The Dust region, and to the objectives area. We should take note that on our way to the church from Boot Hill, the only opponents we encounter are spiderants.
When we reach the church we have to search the graves in order to find the treasure chest (its in a grave next to the church, on the right side while were facing the building). Digging up the stash will make Mobley come out from the church. Gettle will also appear, meaning that we have to survive a three-way showdown as soon as the bell rings for the third time.
Mobley will start attacking us, while Gettle will start attacking Mobley, so its entirely our choice on how we want to deal with them.
Tip: A good idea is to let them fight, and defeat the winner.
After theyre both defeated, we have to open Mordecais chest. Lots of stuff will come out from it, and this action will also complete the Borderlands 2 The Good the Bad and the Mordecai optional mission; allowing us to focus on other missions featured in Borderlands 2.