Sorcerer's Cave is played underground, while Mystic Wood is above ground. They are definitely a must-have because they are like companion games, though they can't strictly be added together unless you come up with some kind of mechanism to do so. That probably wouldn't be too hard. I think Sorcerer's Cave is probably a little better because of the fact that you can go to different levels underground, whereas Mystic Wood is played on just one above-ground level. Other than that, they are kind of similar. Get both.