Impregnable is a side quest which offers rewards for upgrading the Wall.
| Requirement | Reward |
|---|---|
| Upgrade Wall to Level 2 |  2,500  1,750 |
| Upgrade Wall to Level 3 | 3,250 6,000 |
| Upgrade Wall to Level 4 | 5,250 7,750 |
| Upgrade Wall to Level 5 | 25,250 26,750 |
| Upgrade Wall to Level 6 | 17,500 21,000  9,500 |
| Upgrade Wall to Level 7 | 21,250 24,750 12,250 |
| Upgrade Wall to Level 8 | 26,750 31,500 16,500 |
| Upgrade Wall to Level 9 | 29,250 30,000 17,000 |
| Upgrade Wall to Level 19 | 469,000 548,750 331,250 |
| Upgrade Wall to Level 20 | 704,750 824,250 498,000 |
| Upgrade Wall to Level 22 | 1,585,750 1,856,500 1,122,250 |