When used, it allowed a city to recruit a powerful NPC soldier with high Growth Potential. Meanwhile, the better-developed a city was, the greater the City Conscription Order's effects would become.
In the past, there was one Guild that actually managed to recruit a Tier 4 Great Wizard through a City Conscription Order, when it was normally extremely rare for a city to manage to get even a Tier 2 NPC soldier. As for Tier 3 NPCs and above, it was practically impossible to recruit one without external aid such as the Hero's Chapter and the City Conscription Order. Not to mention, a Tier 4 Great Wizard was much more powerful than other classes when it came to defending a city.