Dwarven Allies

First letter
The first letter is obtained from Claptrap.

Second letter
The second letter requires a jumping puzzle. Initially, it is impossible because of the missing platforms. However, Tina will quickly add the necessary platforms as needed.

If you keep missing the jumps, Tina will construct a bridge for you.

Solve Ancient Dwarven Puzzle
This puzzle is a simple remember the sequence - when the cube is activated and lowered, note the order at which the bolts of lightning rotate a side of the cube. use the side crystals in reverse order.

If you miss the puzzle the first time around, you will receive an optional objective to punch the puzzle. This has the same result as solving it.

Fourth letter
The last letter requires a boss battle against the Gold golem.

You can optionally clear the curse by shooting the strange mug, resulting in the dwarf to offer you the letter for free. However, he recognizes you as the one you killed the king, and continues with the attack.