Dragon Quest IX: Sentinels of the Starry Skies/Post-Game

Welcome to the post-game. If you thought the game would end after the credits rolled, you couldn't be more wrong. Not only is there collecting and cataloguing to be done of items, monsters, alchemy recipes, and accolades (if you're the type for that sort of thing) there are close to two hundred quests for you to take on, some of which advance the story, and literally millions of grottoes to explore. Here's how you should get started:

Regain access to the Starflight Express
Zoom to Port Llaffan and speak to Jona Jones. She claims that the Leviathan is still around, but she has no idea how to summon it. It's up to you to find out. Head to the inn and rest to get night to fall (unless night has already fallen upon your return), then head out to the beach near the nets and you will see a ghost. Talk to it and it will detail to you how to summon the Leviathan. The ghost tells you that you need to be wearing/equipped with the following: a watermaul wand, a flowing dress, and a silver shield.

If you need any of that equipment, here's where to find them:
 * Watermaul wand - Gleeba weapon shop (4700 G)
 * Flowing dress - Upover armour shop (18,000 G)
 * Silver Shield - Stornway armour shop (Post-game, 30,500 G)

Return to Jona and tell her what the ghost told you. She will then head to Tywll Cave and wait for you. Once you've obtained the equipment make your way through the cave, to the endpoint where you previously faced the Leviathan. Equip one of your party members with all three pieces of equipment and speak to Jona.

The Leviathan reappears and a grueling battle ensues if you're not properly leveled (mid fifties should make things easier). Once you defeat the Leviathan, you receive a fygg. Eating it restores your access to the Starlight Express and subsequently allows access to any and every area around the world.

You need a treasure map before you start spelunking!
There are multiple ways to get treasure maps in the game, but the easiest way to get yourself started is to go and talk to King Schott of Stornway or complete quest #15 (all you need to do is give a man up near Zere Rocks some special medicine). Once you have your first map or two you can gain more simply by clearing those grottoes. An in-depth explanation of grottoes and treasure maps can be found in the Treasure Maps and Grottoes page.