After meeting Aunt Maria and her awful husband Jack, you decide to help poor Nadine find her daughter Mary.
Before going into the condemned mine, you might want to fight monsters in the area to level up.
Also, you can find a magic potion in a screen south of Terris where the trees form an upside-down V. Burn the following tree to reveal a staircase that leads to a treasure chest with a purple potion inside.
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There is another potion that you can find by going east from the condemned mine until you are along the coast, then go north up a narrow strip of land to find another purple potion.
There is also a megapotion if you go west and slightly south from Goodheart Castle. You will find a giant pillbug guarding a chest. It is fairly easy to avoid the giant pillbug. If it chases after you, just exit and go back until the pillbug spawns somewhere where it doesn't notice you.
Back to the Mine
If you don't remember how to get to the condemned mine, just return to Nadine's house in Terris then head south until you reach the mine. Go down the stairs to get into the Condemned Mine. There are some Boncas on this screen. You must defeat them in order to go farther into the mine, although you can exit the mine if you are not ready.
Once you kill the Boncas, go east until you find a man trapped in a room locked with a statue. He'll tell you to ask around town for someone who can teach you the magic to destroy the statue.
There are several other rooms of the mine, many of which contain Boncas. Fight these to get a bunch of gold and experience if you wish.
Get Help for the Caged Guy
Leave the mine and go north. Visit the bar, which is east of Nadine's house. You'll ask for help, and the bartender will say to ask the old guy in the house to the south about magic. As Dink leaves, you see that an agent of the Cast overheard him.
Now visit the house to the south. The door is locked. Just punch the door and you will be allowed in. Talk to the old man to learn the Acid Rain Magic. To use Acid Rain, go to the inventory screen to select the spell.
Free the Caged Guy
Now return to the condemned mine. Defeat the Boncas at the entrance (if any) and then go all the way to the right. Switch to the Acid Rain magic if you haven't already, and wait for it to charge up. Then aim for the statue and cast the spell. If you aimed correctly, the statue will disappear. Be careful not to stand near the spot where you cast Acid Rain, because it will hurt you if you stand in it.
Follow the guy out of the room. Watch the scene. You will receive a magic scroll. Your next step is to deal with Bishop Nelson. Go west of Goodheart Castle.