Reiatsu Core is one of those items in Sailor Piece that every serious player will need eventually, and farming it without a plan is a guaranteed way to waste hours. It drops from a single source, has a low drop rate, and you need four of them just to clear Ascension 4. However, once you know the loop, the grind becomes a lot more manageable. This guide covers exactly where to find it, how to farm it efficiently, and what to do with it once you have enough.
What Is Reiatsu Core and Why Do You Need It?
Reiatsu Core is a Legendary-rarity item in Sailor Piece that serves two specific purposes: unlocking Ascension 4 and crafting the Aizen Sword. Both are significant late-game milestones, so the sooner you start farming, the better.
| Use | Details |
| Ascension 4 | Requires 4x Reiatsu Cores plus additional materials |
| Aizen Sword (Mythical) | Requires 3x Reiatsu Cores as part of the crafting recipe |
Where Does Reiatsu Core Drop?
Reiatsu Core has only one confirmed drop source in Sailor Piece: the Aizen boss, located in Hueco Mundo (also referred to as Hollow Island). There is no alternative farming location and no NPC that sells it directly. Your entire farming strategy revolves around this one boss.
| Stat | Value |
| Boss Name | Aizen |
| Location | Hueco Mundo (Hollow Island) |
| Boss HP | 25,000,000 |
| Respawn Timer | Approximately 5 to 7.5 minutes |
| Reiatsu Core Drop Rate | 3% |
| Item Rarity | Legendary |
To reach Hueco Mundo, use the Sailor Piece map portal. Note that you generally need to complete the Hogyoku Quest (or the equivalent early Soul Society progression) to fully unlock Hueco Mundo travel via the portal. Make sure you have completed this step and levelled up sufficiently before heading there, as it is a late-game area.
Critical rule: You must deal at least 10% of Aizen’s total HP (2,500,000 damage) in a single fight to qualify for any drops, including the Reiatsu Core. Many new players miss this requirement entirely and receive no loot despite participating in the fight.
Aizen Drop Table
Understanding the full Aizen loot table helps you manage expectations and recognise when a run has been successful, even without a Reiatsu Core drop.
| Drop | Drop Rate |
| Haki Color Reroll | 100% |
| Race Reroll | 85% |
| Trait Reroll | 75% |
| Boss Ticket | 45% |
| Dungeon Key | 30% |
| Mirage Pendant | 20% |
| Illusion Prism | 8% |
| Reiatsu Core | 3% |
| Manipulator (Title) | 2% |
| Aizen Haori | 2% |
| Hogyoku Fragment | 1.2% |
Aizen also applies buffs to himself during the fight: 40% increased damage output, 50% increased defense, and 15% incoming damage reduction. Factor these into your DPS planning before the fight begins.
How to Farm Reiatsu Core Step by Step
Once you are in Hueco Mundo, the farming loop is straightforward. The key is consistency and minimising downtime between runs.
- Travel to Hueco Mundo via the map portal and locate the Aizen boss directly in front of the dome building.
- Engage and defeat Aizen. Use your highest DPS build to bring him down as quickly as possible. Remember that you must personally deal at least 10% of his total HP to qualify for drops.
- After defeat, check your loot. If the Reiatsu Core does not drop, do not leave the area.
- Wait near the boss spawn point for the respawn timer, which ranges from approximately 5 to 7.5 minutes depending on the server.
- Repeat immediately on respawn. Staying near the spawn location eliminates travel time and keeps your runs tight.
Pity system tip: Every 25th boss you defeat (any boss across the game) guarantees a rare drop. Smart players farm 24 easier bosses first, then fight Aizen as their 25th kill to benefit from the guaranteed rare drop on that attempt, significantly improving their chances of landing the Reiatsu Core.
Tips to Farm Reiatsu Core Faster
A 3% drop rate means both patience and optimisation matter. These confirmed methods will help you improve your results:
Boost Your Luck Stat
Higher Luck improves drop probabilities across all RNG-based items. Three of the most effective Luck boosters in Sailor Piece are:
| Method | Luck Bonus |
| Fortune Rune | +15% Luck |
| Destiny Mark Title (requires defeating 2,500 bosses) | +40% Luck |
| Kitsune Race | +25% Luck |
Stacking all three provides a significant cumulative improvement to your drop chances across a full farming session.
Use a High DPS Build
The faster you defeat Aizen, the more attempts you can complete per hour. Focus on builds or swords that maximise consistent damage output rather than burst that does not account for his damage reduction buff. Consistently dealing above the 10% HP threshold as quickly as possible is the priority.
Farm in a Group
Group farming is by far the fastest method available right now. A well-coordinated squad can clear Aizen significantly faster than a solo run, which increases the number of attempts you complete before each respawn. Solo farming is possible, but it is considerably slower, so finding a reliable group is strongly recommended.
Keep Abilities Off Cooldown at Spawn
Prepare your skills in the final seconds before each respawn so you can immediately deal maximum damage from the very start of the next fight.
Use the Pity System Strategically
As noted above, your 25th boss kill across the game guarantees a rare drop. Track your boss kill count and plan your Aizen attempts to land on that 25th kill whenever possible. This takes some coordination but meaningfully improves your farming efficiency over a long session.
What Is Reiatsu Core Used For?
Ascension 4
To complete Ascension 4, you need the following:
- 4x Reiatsu Cores
- 1x Blood Ring
- Use any ability 500 times
- Clear the Shadow Dungeon on Medium difficulty 10 times
- Defeat 625 NPCs
- Deal 1 billion total damage
- Defeat 50 bosses
The permanent rewards from Ascension 4 are worth the grind: +10% Gems, +5% Luck, and 2% Cooldown Reduction. These bonuses stack with earlier Ascension rewards and improve your farming efficiency going forward. You initiate the Ascension process by speaking with the Ascensions NPC on Sailor Island, identifiable as the Killua character.
Aizen Sword (Mythical Rarity)
The Aizen Sword is one of the stronger weapon options in Sailor Piece. You can unlock it by speaking with the Aizen Trainer NPC in Hueco Mundo once you have gathered the full crafting materials:
- 3x Reiatsu Cores
- 10x Mirage Pendants
- 6x Illusion Prisms
- 1x Hogyoku Fragment
- 10,000 Gems
- 6,000,000 Gold
After providing the materials, five quests unlock in sequence:
| Quest | Requirement |
| Quest 1 | Defeat 250 Hollows |
| Quest 2 | Unlock the Shinigami Race (1% drop via Race Rerolls) |
| Quest 3 | Use a Worthiness Fragment (note: 25% chance this quest fails) |
| Quest 4 | Deal 350 million total damage |
| Quest 5 | Defeat the Aizen boss 15 times |
Completing all five quests rewards you with the Aizen Sword. The Aizen Sword is also a prerequisite for crafting True Aizen, a stronger weapon available through the True Aizen Trainer NPC at Soul Society. However, the True Aizen boss does not drop Reiatsu Cores, so fighting him is not necessary for this farming goal.
Can You Get Reiatsu Core Through Trading?
Yes. If farming Aizen directly is proving difficult or slow, Reiatsu Core is obtainable through the in-game trading system. Because of its Legendary rarity, players typically ask for high-value items in return. Use the Trading option to initiate a deal, and always double-check both trade windows before confirming the exchange, as trades are final.
Reiatsu Core at a Glance
| Question | Answer |
| Where does it drop? | Aizen boss in Hueco Mundo (Hollow Island) |
| What is the drop rate? | 3% |
| Minimum damage required for drops? | 10% of Aizen’s HP (2,500,000 damage) |
| Is there a pity system? | Yes, every 25th boss kill guarantees a rare drop |
| How many do you need for Ascension 4? | 4x |
| How many do you need for the Aizen Sword? | 3x |
| Can you trade for it? | Yes, via the in-game trading system |
| How often does Aizen respawn? | Approximately every 5 to 7.5 minutes |
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