First you need to solve quest number 39 to gain ability to fly. See this to know how to solve the quest. After you solve that quest go to Stornway, you can buy new armor and weapon from extra merchant in each shop (Gigant armor is nice :D).
Now Fly to Tower of Nod
It is located near Coffinwell and you must have ability to fly in order to reach it.
|killing machine||iron nails||1880|
|freezing fog||ice crystal, sage’s elixir||1360|
|splatterhorn||magic beast horn||980|
|swinoceros||magic beast horn||610|
|metal king slime||slime crown||120040|
The dungeon is pretty straightforward. You can get decent amount of experience here, many enemy groups give you about 2000-4000 exp to one character. There is also metal king slime in this place but it is very rare and very hard to kill. Metal king slime has about 12-14 HP, so good luck when you are trying to kill it.
Tips by Tuppup:
Metal king slimes can be easily killed with spear skill Thunder Thrust and axe skill Hatched Man. Both attacks are always critical, so if you manage to hit, it’ll be 1 hit kil
Just keep go upstairs until you reach L7. In L7 you can climb the vine to find sleeping Chimaera. For now you can’t do anything to it because the quest is still locked at the time I write this guide (need wi-fi).
So just exit this dungeon and you have beaten bonus dungeon in dragon quest IX. Now it is time to grind your character’s level in grotto and hunting ingredients for perfect equipment.
Other thing you can do after that:
I think that is all you can do after finished the game. Will update this guide when I found optional BOSS in normal map (I heard there is one in small snow island).