Neverness to Everness Guide: How to Beat Sea Prisoner

Quick Answer: To unlock the Sea Prisoner boss, reverse a four-wheeled car into Nautili Tunnel and complete the chase sequence. Bring an Anima-focused team to exploit its weakness, dodge the Phase 2 ground hazards, and parry its aerial dash to secure the powerful S-Tier Song of the Whale Arc.

How to Unlock the Sea Prisoner

The Sea Prisoner doesn’t just sit on the map waiting for you. You actually have to trigger a specific Anomaly Commission called Deep Blue Sorrow.

Here is the exact sequence to force the boss to spawn:

1. Grab any four-wheeled vehicle. Motorcycles absolutely will not work.
2. Drive to the Bridge Crossing district and find the Nautili Tunnel.
3. Shift into reverse and back your car into the tunnel. Driving in normally does nothing.
4. A massive whale entity will appear. Follow it through a high-speed chase until you reach the icy arena.

Once you complete the initial unlock, the boss permanently relocates east of Cape Square in the New Herland District for future rematches.

Exploiting the Sea Prisoner’s Weakness

This boss is completely weak to Anima damage and has zero built-in resistances. If you want to melt its health bar quickly, build your team around the Blossom and Charge Esper Cycles. This specific loop keeps your Ultimates constantly charging.

Here are the two best team compositions for the job:

Nanally Hypercarry Team

Hathor Charge Team

Phase Mechanics and Parry Timings

The Sea Prisoner is massive and slow. That plays right into your hands. During Phase 1, just watch for the red glint before it attacks. It telegraphs everything clearly, so dodge when you see the flash rather than guessing the timing independently.

At 70% health, Phase 2 kicks in. The arena starts raining, and the boss drops predictive circles on the ground that explode into geysers and whirlpools. Get out of the circles instantly.

The most dangerous move in its entire kit is an aerial dive bomb where it rockets horn-first right at your face. Do not just dodge this. You need to parry it. Landing a successful parry leaves the boss stunned and completely vulnerable for a massive damage window. If you find yourself dying repeatedly, bookmark our How to Beat Sea Prisoner guide to ensure you aren’t missing any crucial positioning cues.

Massive Loot: Song of the Whale Arc

Beating this boss the first time hands you the Song of the Whale, an incredible S-Tier Plasma Arc.

This Arc is an absolute monster on Break-focused builds. It turns your shattered enemies into massive health packs, keeping you alive in endgame content without needing a dedicated healer.

All Fight Rewards

Your first clear drops a massive pile of progression materials. Here is what you get:

• 40 Annulith
• 80 Silver Carrota
• 5 Anomaly Material Selection Boxes
• 30 U-ONE
• 7,500 Beetle Coins

If you run the boss again later to farm, you will net a repeatable 300 Hunter EXP and 6,000 Beetle Coins per clear.

For more character builds, optimal team compositions, and boss strategies, check out my other guides.