Dark Cloud

Play in Demon Shaft hard dungeon
Finish the entire game and save.
Jump to "Go To Other Areas" map, to select Demon shaft to play.

Get Rare Weapons:
When you defeat The Moon Sea and go to Dark Heaven Castle, go to the 1st floor
(5 years ago) and find a big chest. If it's not the clown, then it's usually
a rare weapon like the Lamb Sword.

Ultimate Dagger:
Upgrade dagger into level 5. Then do status break. You'll get the synth sphere,
and your dagger will still be there! Then all you have to do is put the
sphere on the original dagger.

Sun Sword:
Complete Toto's house. To complete you need:
Toto, Golem, totam pole, and the handle.
At the event, Golem will turn himself into the Sun Sword.
After a couple of Synthespheres, the Sun Sword is unstoppable!

Get the Chronicle Sword:
First get the chopper dagger. Upgrade into a gold dagger. After, upgrade it
into the maneater. Next time upgrade it into the Atlamillia Sword.
Upgrade it one more time and you have the second best sword in the game.

Easy money:
Go into the divine beast cave. Pick lots of prickly fishing bate and sell it.