The "Dark Syndicate Saga" (暗いシンジケート冒険談) is a saga that follows the Straw Hats as they wander into a piece of the New World under the lordship of a cabal of powerful crime lords, the eponymous Dark Syndicate. During the saga, the Straw Hats unintentionally get involved in the plans of a race of machines called the Automatons, in their aspirations for world domination. It is made of six arcs.
Not long after stumbling upon an island, they meet up with a mercenary named Isabella, and learn that the island is under the dominion of Crimson Claw. After Luffy defeats its leader, Gusano, the Straw Hats learn about the existence of the larger Syndicate from Isabella, and how Zero has taken control of her homeland. The Straw Hats then decide to help Isabella out, and to go to Acero.
As they travel to Acero, they accidentally intercept the tribute the Forty Thieves are sending to Hierro. This attracts the attention of the order, as well as Hierro, who send its top enforcer, Timor Salamander to address the issue. The Straw Hats engage their enemies, and after Luffy defeats Salamander, and Nami defeats Slash, they move on.
By this point, the Straw Hats now have Hierro's full attention. Deciding to deal with them more directly, left-lieutenant Mariposa Esquerda orders the Ancient Sea Pirates to deal with them, as well as sending two mercenaries after them. The prehistoric pirates and the mercenary engage the Straw Hats, but are also defeated by them. Now having the attention of Zero himself, he sends one of the Pirate Titans, Messorem, to deal with them. Instead of defeating them, Messorem instead veers them off course, to Mad Land.
There, they engage another member of the Syndicate, Wonderland, and its leader, Isaac Wonder. While they manage to defeat it and its leader, as they're leaving they are interceted by all five of the Pirate Titans. All at once, they engage the Straw Hats, who are badly wounded in the fight, and are forced to flee.
The Straw Hats split up, with Luffy, Nami, Jinbe, and Brook going to Acero with Isabella, as the rest of the crew stays on the Sunny. Meanwhile, Zero summons the whole of the Syndicate, including its associates, to Acero for the first Dark Summit in years.
- Crimson Claw Arc
- Forty Thieves Arc
- Ancient Sea Pirates Arc
- Wonderland Arc
- Acero Arc
- Automaton Arc