NPCs

NPC stands for non-player character, this characters are often given to players as a reward for completing an event, or getting certain ammount of points in it, there are two types of NPCs

Permanent NPC
a permanent NPC is an NPC that will stay in your city forever giving a certain bonus, that could be by example
 * 1) free troops every given period of time
 * 2) a bonus to the stats of some unit
 * 3) free orders or materials every given period of time

Non-permanent NPC
a non permanent NPC is a non player character that will leave your city after given ammount of time, most of this can come from the tavern, they will give certain bonus for some time and then go, but events sometimes also offer them as a reward, and sometimes they will act like the permanent NPCs that give free troops every certain ammount of time, but this ones will go away

example: nikolay raevsky, hired in tavern, will boost troops training speed by 35% and will leave player's city after 30 days, costs 40 contracts, can be re-hired once he goes away