Niffelheim

The trophy description for this one is a little misleading. The same requirements that applied for Faithful Servant apply here. The Quest must be given to you by a Priest.

You can check your progress towards this trophy by checking your Quest Log (, scroll with until you get to the Quest Log, then count the Priest Quest that show 'completed'). For the most part, they will be about collecting raw materials (Mushrooms, plants etc.). If you don't have any active Priests Quests in your log, you can manually pick one up from the Priests in the underground area. They're located in the top-most open room (around levels 4-5):

Just talk to them to pick up a new Quest. Each Priest in each Dungeon/Cave will give you a unique quest so if you have one you don't wish to do, talk to another Priest to get a different one. As long as you're actively working on your Quests as you work on upgrading your buildings, you'll be able to get this well before you hit 100 Days played. Once you completed your 10th Priest Quest, the trophy will unlock.