Original creator of quests invented quests to be obtained only in villages and you get them by rolling dice - by rolling black you "upgrade" the quest (take a quest from different deck) and you keep rolling until you reach unique quests or you fail to roll black.
I hate dice rolling - it takes too much time, so I changed those rules in time.
I'm not sure if I posted those rules here but I'm using them now as you get the higher quest if you completed lower rank quest before, so to get unique quest you need to complete city quest etc...
And you are able to get those quests also in other locations, that's why I used "town" in quests cards, as using village word in monasteries would be wrong.
Unfortunately I don't have that much free time to improve the deck as I wanted to do it and I left them as they are now.
Feel free to use any rules you want for those quests - it's not official so don't look for any rules
Create them as you think they'll work for you.