Happy Dungeons
42 Achievements
1,250
200-240h
The Unbearable Lightness of the Dungeon
100 hours played.
50
0.13%
How to unlock the The Unbearable Lightness of the Dungeon achievement in Happy Dungeons - Definitive Guide
However, if you want the set of time played achievements quickly, the method that you can use for each of the play 10 hours as the three classes achievements works here as well. When you finish a level, rather than go through the door and seeing your rewards from the level, just let it sit. The timer will have stopped at this point, but the game will continue counting the time spent for these achievements. Do this for just over four days and you will have "played" for over 100 hours.
Note: You must finish the level for this time to count. You won't make any progress if you do not go through the final door after you are done idling.
This will more than likely be the last trophy you get since you should be able to get the rest of them before you reach the requirements for this one. The crappy part about this trophy is that while it requires you to play the game for 100 hours, the game only counts you as "playing it" is when you are doing story mode stages or the infinite dungeon and actually playing when the timer is going. The other bad part is that it doesn't count your time if you fail a mission, only if you complete it successfully.
The workaround I have found for this is to create a session in the infinite dungeon and pick any of the areas from Greedy Pig's Room (B11) or lower on the list (make sure that you are alone when playing and no one else joins in or else they can screw this up). When you start off those areas you will be put in a room with a rope/elevator exit in them. Each of them has a 45 minute time limit, so start it up and let the timer get down to a minute or so and then exit out via the rope or elevator. When the results screen comes up, it will count as a successful mission and count towards your overall time. This is also an easy way to get the character related time trophies as well as you can just select a different character each time you do. Just keep rinsing and repeating those steps and once you reach 100 hours, the trophy will pop.
NOTE: There is another, easier method to getting the 100 hours required. Just complete any quest and when you finish it, the timer for the stage will stop counting down. Once it does, just have your character stand around instead of going through the final door as it the play time counter will still be going up. When you are ready, just exit through the final door and you will see that however long you were standing there will have counted towards your overall play time. (Thanks to rpg49ers for the tip!)