The Phantasm Core is a mythical-rarity material in Sailor Piece that serves as the key ingredient for unlocking the King of Heroes fighting style — one of the strongest AoE-focused combat options in the game. It cannot be purchased with Robux or obtained from any other boss. The only path to getting one is repeated kills of the King of Heroes (Gilgamesh) on Boss Island.
Quick answer: Defeat the King of Heroes boss on Boss Island. The Phantasm Core has a 0.5–0.75% drop chance per kill, and you must deal at least 10% of the boss's total health in damage to qualify for any loot.
How to Summon the King of Heroes
The entire process takes place on Boss Island. You reach it through the portal located on your current island. Once you arrive, the Boss Summoner NPC stands directly in front of the portal exit.
Step 1: Interact with the Boss Summoner NPC to open the boss selection menu. Scroll through the list until you find King of Heroes, then select your preferred difficulty level.
Step 2: Pay the summoning cost. Each spawn requires 1× Divine Grail, 500,000 money, and 500 gems. If you don't have a Divine Grail on hand, you'll need to farm one before attempting the fight.
Step 3: Click the Spawn button. Gilgamesh will appear on Boss Island, and you can engage immediately.
Summoning Cost Breakdown
| Resource | Amount per Summon |
|---|---|
| Divine Grail | 1 |
| Money | 500,000 |
| Gems | 500 |
Because the drop rate sits between 0.5% and 0.75%, expect to burn through a significant stockpile of Divine Grails, money, and gems before the Phantasm Core appears. Farming these resources in advance saves time between attempts.
Farming the Phantasm Core Faster
King of Heroes is a late-game boss with massive health and punishing damage output. Solo attempts are possible with a strong build, but grouping with other players speeds up each kill cycle considerably. The catch is that you still need to personally hit the 10% damage threshold, so don't rely entirely on teammates to carry the fight.
Sailor Piece boss raids reward higher damage dealers with better loot qualification. Prioritize a high-damage build using top-tier swords, devil fruits, and fighting styles. The stronger your output, the more likely you are to land in the best reward bracket each run.
Luck-boosting mechanics also matter. Equipping titles, races, clans, and runes that increase drop luck can push the effective drop rate slightly higher. Every fraction of a percent counts when you're grinding a sub-1% item.
If other players on your server are focused on different bosses and the King of Heroes queue feels slow, hop between servers. This lets you skip idle time and get into fresh boss spawns more quickly.
What the Phantasm Core Unlocks
The Phantasm Core has two confirmed uses, both of which are significant for endgame progression.
King of Heroes Fighting Style
To unlock this fighting style, interact with the King of Heroes NPC on Boss Island and submit the following materials:
| Requirement | Amount |
|---|---|
| Phantasm Core | 1 |
| Ancient Shards | 6 |
| Throne Remnants | 12 |
| Golden Essence | 3 |
| Gems | 22,500 |
| Money | 25,000,000 |
| Golden King title | Required (must already hold it) |
The King of Heroes fighting style delivers strong area-of-effect attacks, making it effective for clearing groups of enemies and farming rarer drops across the game. It's widely considered one of the best damage-dealing styles available.
Ascension Level 8
Reaching Ascension 8 in Sailor Piece requires 2× Phantasm Cores along with 3× Slime Cores and several additional tasks. Ascending to this level provides a meaningful boost to both your damage output and your drop luck, which compounds the value of every boss fight going forward.
Since Ascension 8 demands two Phantasm Cores rather than one, plan for an extended farming window if you intend to unlock both the fighting style and this ascension tier.
Other Gilgamesh Drops Worth Tracking
While you're repeatedly fighting the King of Heroes for the Phantasm Core, several other items will drop along the way. Knowing their rates helps you gauge your overall progress.
| Item | Rarity | Drop Rate |
|---|---|---|
| Throne Remnant | Epic | 11.5–20% |
| Ancient Shard | Legendary | 4.5–6.5% |
| Golden Essence | Legendary | 1.5–2.5% |
| Phantasm Core | Mythical | 0.5–0.75% |
Throne Remnants drop frequently enough that you'll likely have more than the 12 needed for the fighting style well before the Phantasm Core shows up. Ancient Shards and Golden Essence accumulate at a moderate pace, so keep an eye on your inventory to know exactly when you're ready to turn everything in.
Can I buy the Phantasm Core with Robux?
No. The Phantasm Core cannot be purchased with Robux or any premium currency. The only way to obtain it is by defeating the King of Heroes boss and qualifying for the drop through the 10% damage threshold.
The Phantasm Core grind is one of the longest in Sailor Piece, but the payoff — a top-tier fighting style and access to Ascension 8 — makes it one of the most impactful farms in the game. Stock up on Divine Grails, bring your strongest gear, and settle in for the long haul.