How to Get the Atomic Core in Sailor Piece (Roblox 2026 Guide)

If you are trying to reach the absolute endgame in Roblox Sailor Piece, you will inevitably hit a wall until you secure the Atomic Core.

Many players mistake the Atomic Core for a usable weapon. It is actually a highly coveted, ultra-rare crafting material. Its sole purpose in the game is to serve as the main ingredient for unlocking the legendary Shadow Sword (Cid V1).

Here is exactly how to farm it, craft your sword, and prepare for the final endgame grind.

How to Get the Atomic Core

To get your hands on this material, you need to gear up for some heavy PvE grinding. The Atomic Core is exclusively found as a boss drop.

1. Head directly to Dungeon Island.
2. Locate and speak to the Dungeon Master NPC.
3. Enter the CID Dungeon.
4. Fight your way to the end and defeat the final dungeon boss.

The core is not a guaranteed drop. You will likely need to run the CID Dungeon multiple times to finally secure the item in your inventory. (If your level is too low to survive the dungeon, check out our Sailor Piece leveling guide to max out your stats first.)

How to Craft the Shadow Sword (Cid V1)

Once the Atomic Core finally drops, do not leave Dungeon Island. You need to find the Shadow NPC to craft the Shadow Sword.

Having the core is only the first step. You must also roll the Shadowborn Race using the game’s race reroll system. Once you have the correct race, you must hand over the following materials to the NPC:

Material / Requirement	Quantity Needed
Atomic Core	1
Shadow Essence	4
Void Seed	8
Umbral Capsule	20
In-Game Money	10,000,000 (10M)
Gems	15,000 (15K)
Player Race	Shadowborn

(Running low on rerolls or gems? Grab the newest free spins from our updated Sailor Piece codes list.)

Upgrading to the Atomic Sword (Cid V2)

The Shadow Sword is incredibly powerful, but it is also a stepping stone. Owning it is a strict prerequisite for unlocking the game’s ultimate weapon: the Atomic Sword (Cid V2).

Once you have the Shadow Sword equipped, sail to Lawless Island. Here is your endgame progression loop:

1. Farm the Arena Fighters scattered around the island.
2. Collect Abyss Sigils from their drops.
3. Use those sigils to summon the Atomic Boss.
4. Defeat the boss repeatedly to collect ultra-rare endgame materials like the Atomic Omen and Eminence Essence.

Fastest Dungeon Farming Tips

Clearing the CID Dungeon repeatedly can be tedious. To drastically speed up your runs, equip high-damage, massive AoE (Area of Effect) Devil Fruits to wipe out mobs instantly. (See our Sailor Piece fruit tier list for the best dungeon-clearing fruits).

Alternatively, squad up with max-level players to carry you through the boss room in seconds. Do check the official game updates for new swords.

Frequently Asked Questions (FAQ)

Where is the Dungeon NPC located?

The Dungeon Master NPC is located on Dungeon Island. You must speak to him to access the CID Dungeon and farm the core.

What race do I need for the Shadow Sword?

You must have the Shadowborn Race active when speaking to the Shadow NPC. You can obtain this by using race rerolls.

Can I buy the Atomic Sword with Robux?

Yes. If you want to bypass the massive grind for the Atomic Core, the Shadow Sword, and the final boss materials, you can purchase the Atomic Sword directly for 1449 Robux.