Shipwreck Abs Farming Location - Dark Cloud Guides
The best leveling location in all of Dark Cloud is the Back Floor area of Layer 14 in the Shipwreck dungeon. On this Back Floor you'll find nothing but Mask of Prajna enemies, these guys are easy to take out with melee characters but ranged will have a bit more trouble. There will be a total of 8 enemies here which will each give you 24 Abs per kill for a grand total of 192 Abs per full clear.
In my opinion the Werewolf location in the Wise Owl Forest is a better spot for grinding Abs since the Werewolf enemies are easier to defeat for both melee and ranged characters. They also give the same amount of Abs per kill and there is the same amount of enemies on the Back Floor. However, the main difference between these two locations is you can't buy the item required for entering the Back Floor from a vendor when it comes to the Wise Owl Forest.
Most people consider this location in Shipwreck to be superior because you can buy the Flapping Fish needed to access this Back Floor from Ruty's Store right in Queens. This means you can farm this Back Floor whenever you'd like and you never have to go out of your way and grind hoping for a Back Floor item to be inside of a chest.
Aside from this single reason, I would argue that this Back Floor is inferior to the Wise Owl Forest. The Werewolf enemies in Wise Owl Forest hit for a lot less which gives you more margin for error when leveling up (especially with characters you aren't good at playing) and they are a lot easier to defeat using a ranged character.
One thing to note in this guide too is once you unlock the Back Floor and clear it simply go back to the big fish that brought you here and ride him back to the normal floor. Return to the Back Floor again and all of the enemies will have respawned. You can do this as many times as you'd like to reset all of the enemies on the Back Floor without ever leaving the dungeon.
Doing it this way, however, will not respawn any of the Treasure Chests. The only way for you to respawn all of the chests is to leave the dungeon, buy a new Flapping Fish then enter it again. I've personally farmed this Back Floor both ways quite a bit, when I need some Attachments I usually will clear the Back Floor, teleport out and buy a new fish then return to clear it again.
If you'd like to learn more about upgrading weapons in Dark Cloud and which are the best weapons for each character in this game I recommend you check out my Dark Cloud Ultimate Weapons Guide. You should know what weapons are the best for each of your characters before you start evolving them up into different things. Not every 'final tier' weapon is made equally and some are significantly better than others.