Dandon defeated the advance force, but decided the people of Vylens would be safest hiding in the nearby caves. The enemy's planned reinforcements came and destroyed the town; now you must rebuild - and prepare to defend against his main army. Some of the defenses have been rebuilt by masons, and you must also repay them in kind.
Beware that on Very Hard the standard win conditions are strictly impossible. See readme notes for an alternate challenge.