"Cult of the Vault" is a challenge from Tiny Tina's Assault on Dragon Keep DLC.
This Challenge, as of 8/15/13, is bugged. Symbol 2 is inaccessible but it exists inside the game so it counts toward the total
The First symbol is found in Ingot Processing in the Southern portion of the mines through Wizard's Crossing and Stonecrag Ridge. Head Southeast from there to get into Ingot Processing. Once in there head for the first break on the Eastern side, up the sets of stairs between buildings. You will find the symbol without any trouble there.
The Third Symbol is found in Ingot Processing where you fought Greedtooth, the Gold Golem. Head over to the tower in the Northeastern part of the area and look on the Northern side of it. Move carefully along the edge to avoid falling in the lava. When you make to the Northern face, you will find it on the wall there.
The Second Symbol is technically found in the Gilded Forge. Head over to the Western side of it and if you can get into the inaccessible alcove to the South of the D20 Chest, then you can get this. The statement above is incorrect, just enter the combo on the giant dice backwards.
Ranks and Rewards
Badass Ranks: 5