After
Open up your map with
, and sail to the pink dot. In this area, head north, over the bridge and into Dundrasil. The enemies in this area are a step up from what you've been facing, so you may want to grind a few levels. Reaching level 19 and learnign midheal with the hero would be wise. Make sure you have the best armor and gear on your hero, too. Head north to Octagonia. Enter Octagonia for a cutscene, then walk forward into another cutscene. Go and speak to the man at the desk in front of you. Go right around the circle and down into the center. Talk to the man in the yellow hood to enter the arena.
You can rest for free on the right, or go up to the arena on the left in the waiting room. When you head up, there will be a cutscene. Go back down the elevator, and walk around the circle for a cutscene. After this, go right to the inn. Sleep and you'll wake up in a cutscene. At the end, you'll be back in the waiting room, go talk to Vince. Now, you'll be in your first fight. When the Showman makes copies of himself, let Vince attack one first, he knows which is the real one. Take out Showman and then Underdigger. Defeating them is pretty easy and will start a long cutscene. Walk around the circle for another cutscene. Turn right, go down the stairs and into a cutscene. Follow Vince for a cutscene. Head up the stairs, through the church and into Vince's room for another cutscene.
This brings you back to the waiting room. Go talk to Vince. In this fight I mostly focused on healing myself, and let Vince deal damage. Hit Sinderella when you can. She can heal, too. With Sincerella down, Whambelina is an easy fight. After a cutscene, you'll go right into a fight with Sylva and Golden boy. There's not much to say about this fight.
Another cutscene will lead you to a fight with Rab and Jade. Vince will fall asleep and there's nothing you can do about it. Rab can heal, too. Take out Rab to stop the healing. You may just have to wait for him to run out of MP. Defeat Jade as well to get a cutscene. Rest at the inn.
After speaking to Rab, return to the Orphanage, and head left down the stairs. Continue downstairs into a cave. In this dungeon, watch out for surprise monsters. The toxic Zombies are really dangerous--Use Serena's Squelch spell if they poison you. The zombies are weak to fire, so use Veronica's Fire spells to kill them quickly. At the point where you see two chests next to each other, the right one is a mimic. Head to the southwest corner of the map, where there is a ledge you can jump up to. There will be a cutscene and then you'll fight the boss. This boss is slightly weak to fire. However, poison using Erik is also effective.
After the cutscene, you'll wake up at the inn, go and talk to the guy at the desk for another cutscene. Then, you'll have to fight Vince one-on-one, but he won't fight back. After this last cutscene, you'll unlock the achievement.