Impregnable is a side quest which offers rewards for upgrading the Wall.

Impregnable — Upgrade the Wall (edit)
Requirement Reward
Upgrade Wall to Level 2 Resource icon food 2,500
Resource icon wood 1,750
Upgrade Wall to Level 3 Resource icon food 3,250
Resource icon wood 6,000
Upgrade Wall to Level 4 Resource icon food 5,250
Resource icon wood 7,750
Upgrade Wall to Level 5 Resource icon food 25,250
Resource icon wood 26,750
Upgrade Wall to Level 6 Resource icon food 17,500
Resource icon wood 21,000
Resource icon stone 9,500
Upgrade Wall to Level 7 Resource icon food 21,250
Resource icon wood 24,750
Resource icon stone 12,250
Upgrade Wall to Level 8 Resource icon food 26,750
Resource icon wood 31,500
Resource icon stone 16,500
Upgrade Wall to Level 9 Resource icon food 29,250
Resource icon wood 30,000
Resource icon stone 17,000
Upgrade Wall to Level 19 Resource icon food 469,000
Resource icon wood 548,750
Resource icon stone 331,250
Upgrade Wall to Level 20 Resource icon food 704,750
Resource icon wood 824,250
Resource icon stone 498,000
Upgrade Wall to Level 22 Resource icon food 1,585,750
Resource icon wood 1,856,500
Resource icon stone 1,122,250
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