Infinity Essence is a Mythical-tier material in Sailor Piece tied to the Strongest of Today boss on Shinjuku Island. It gates Ascension progression, the Strongest of Today fighting style, and a key crafting recipe, which makes farming it a required step for mid-to-late game builds.
Where Infinity Essence drops
The Strongest of Today boss is the only source. You summon it at the Strongest Boss Summoner NPC on Shinjuku Island, and each summon costs Limitless Keys. Normal mode uses 1 key, Medium uses 2, and the cost scales upward with difficulty.
Higher difficulties increase the boss HP but also improve reward drop rates. The essence itself is classified as Mythical, so expect multiple clears before one drops on standard mode.
Getting Limitless Keys first
You cannot spawn the boss without keys, so set up a farming loop before heading to Shinjuku. Limitless Keys come from two places, with the boss route being far more reliable.
| Source | Location | Drop chance |
|---|---|---|
| Gojo (Limitless Sorcerer) | Shibuya Station | ~30% |
| Strong Sorcerer mobs | Shinjuku Island | ~0.6% |
Gojo has roughly 4M HP and drops keys frequently. Server hopping after each kill skips the 5–7 minute respawn window, letting you stack 10–20 keys quickly before moving to the summoner.
Defeating the Strongest of Today
Step 1: Travel to Shinjuku Island through the portal and walk straight ahead to find the Strongest Boss Summoner NPC.
Step 2: Press E to open the summon menu, pick your difficulty, and click Spawn. Higher tiers cost more Limitless Keys but award better drop rates.
Step 3: Deal at least 10% of the boss's total HP during the fight. Without that damage threshold, you will not receive any loot, even if the boss dies. The Strongest of Today has roughly 400M HP, so team play is fine as long as you hit the contribution minimum.
Step 4: Collect drops from the kill screen. If Infinity Essence does not appear, summon again and repeat.
Drop rates and difficulty scaling
Reported drop rates for Infinity Essence fall in the 0.65%–0.9% range on lower tiers and climb toward roughly 3.82% on higher difficulty spawns. Because the range is tight and the grind is long, any luck modifier matters.
| Drop | Rarity | Drop chance from Strongest of Today |
|---|---|---|
| Infinity Essence | Mythical | 0.65%–0.9% (higher on upper difficulties) |
| Blue Singularity | Legendary | 2%–3% |
| Six Eye | Legendary | 6%–8% |
| Reversal Pulse | Epic | 15%–25% |
What Infinity Essence is used for
The essence has three concrete uses, and you will likely need several copies across progression.
| Use | Cost in Infinity Essence | Other requirements |
|---|---|---|
| Ascension Level 7 | 2 | 2 Cursed Flesh, dungeon completions, other quest steps |
| Unlock Strongest of Today fighting style | 1 | 3 Blue Singularity, 9 Reversal Pulse, 6 Six Eye consumed, Strongest Sorcerer title |
| Craft Infinity Domain Shard | 2 | 6 Cursed Talisman (submitted at the Infinity Domain Shard NPC) |
Farming efficiency tips
Because the drop rate is low, the practical grind depends more on loop speed than on any single run. A few adjustments meaningfully cut down total time.
- Stockpile keys in bulk at Shibuya before you start the Shinjuku loop, so you are not constantly bouncing between islands.
- Run lifesteal-focused gear, such as the Celestial Rupture Set, to stay in the fight and push your damage share past the 10% threshold.
- Equip luck-boosting races, titles, and runes. The Kitsune race and Fortune Spec Passive both contribute to rare-drop rolls.
- Prioritize sessions during 2x Luck events when available; doubling a sub-1% rate still matters over long grinds.
- Use AoE attacks on Strong Sorcerer mobs when farming supplementary keys on Shinjuku.
How to confirm a successful drop
When Infinity Essence drops, it appears on the post-fight reward screen alongside any other rolls from that kill and is added to your inventory. If you see the reward screen but no essence listed, the roll simply failed. If you see no reward screen at all, you did not hit the 10% damage threshold and should reduce difficulty or improve your build before trying again.
Past that, it is a volume problem. Keep the key farm and boss loop running, and the Mythical eventually lands.