Adventure Mode is a new mode added to the game on February 2, 2015. Each day starting at 9:00 a.m., the player can run a "dungeon" to earn keys. Keys can be redeemed for prizes.
The daily dungeons stay the same from week to week, and different characters are recommended for each one. If you use the recommended character for the day's dungeon, you get a score bonus (but note that it's possible to get an even higher score with a different character if that character is higher level or better equipped than the recommended character).
Monday: Yoke Dungeon, pink keys
Tuesday: Disaster Dungeon, green keys
Wednesday: Destiny Dungeon, blue keys
Thursday: Abundance Dungeon, red keys
Friday: Victory Dungeon, black keys
Saturday: Happiness Dungeon
Sunday: Glory Dungeon
On the weekends, you earn the keys that you have the fewest number of. Keys are redeemed in groups, so you must have at least one of each colour before you can redeem any of them.