Safecracker of Dungeon IIIG 20

I just hit level 75 in the game last night and I can make it down to the 50-60 range in the dungeon. I just use my best deck and don't care if I open a chest or not. If you do care then you have to pay attention to the requirements for each one to unlock the chest. It's just a continuous grind to get this achievement and I login once a day to collect and run down through the dungeon as far as I can. At least once you start getting so far down, the game will automatically start you so far down opening all the chests along the way. So consistently getting farther down in the dungeon will help you get more open chests without having to actually pay attention to the requirements to get them.