Children of Mana Haunted House
First, go to Moti's house and by the fireplace there should be a coat rack. Go up to it and press A. It should say something like, "You got a rusty key."

Go talk to Moti and he will open the house for you. Once inside talk to Tess and she should send you quests about dragons. After you complete all of them, talk to Moti again and he will reward you!

Note I had gotten up to "The Path of Life" before I discovered this secret. I was also at level 40. The opportunity to access the haunted house may not work right away.