I have spent more time hunting Evermoon Seals around Hiisi Island than I care to admit. The newest Nod-Krai zone expansion drops a lot on your plate at once, and if you are like me, you probably want to know exactly what is worth doing before the event window shifts. As of early 2026, the Hiisi Island content cycle feels different from older regional grinds because some rewards are locked behind randomized chest pulls rather than fixed objectives.

What the Evermoon Seal Actually Does

The Evermoon Seal is the key collectible for Hiisi Island. You need three of them to unlock the region's Treasure Vault. They work a bit like the Obsidian Ring found on other islands, but the catch here is that seals drop from select Precious Chests, and some of those chests are not available until you push through story quests or solve event puzzles.

If you miss one seal, do not panic. The game gives you several chest routes across the island, but seal assignment is randomized. That means you might complete a major quest, open a Precious Chest, and not get the seal you were banking on. Backtracking becomes part of the loop.

Main Quest Seal Sources

Your first priority should be these two questlines. They are not optional if you want efficient progress.

“For a Green Island”

Start by teleporting to the Thunderclap Reef – NE waypoint and follow the main quest chain into the cave system.

• Collect quest Fragments as you move through the tunnels.

• Manipulate Kuuhenki Energy to activate mechanisms.

• Interact with the robot NPCs and trigger Moon Mirrors.

• Complete navigation segments and clear enemy encounters.

Each completed segment unlocks a Precious Chest. One of those chests has a chance to contain an Evermoon Seal. Do not skip dialogue or rush pathfinding, because missing a step can lock you out temporarily during the event window.

“The Mirrors, the Maze, and the Tsar”

This one took me longer than expected. Teleport to the waypoint south of the Light-Bathed Platform and drop into the marked pit.

The cave sequence here is more aggressive. You will push and destroy obstacles, deal with Lakkaberries, and solve mirror and energy plant puzzles. The boss-tier Crab Tsar encounter at the end is the real test, so bring crowd control or strong single-target damage.

Two Precious Chests spawn in this quest chain. Once again, Evermoon Seal assignment is randomized. Quest completion also grants additional chests and a Luxurious Chest, so finish the full line even if RNG is unkind early.

Off-Quest Chest Hunting

There are up to twelve Precious Chests scattered across Hiisi Island. At least one off-quest chest can house a possible Evermoon Seal, so do not leave the island the moment your main quest log is empty.

While exploring, watch for Radiant Beasts, block puzzles, Moon Mirror movement challenges, and mob dens. These are not just filler. They contribute to your total chest count and give you more chances at missing seals.

A practical tip from my own run: if you finish both major quests and still only have one or two seals, sweep the coastline and underground cave walls. Some chests sit behind puzzles that are easy to overlook because they blend into the environment.

Opening the Treasure Vault

Once you have all three Evermoon Seals, head to the eastern shore of Frostmoon Enclave. Teleport to the Frostmoon Enclave waypoint and move east. The Vault consumes all three seals when you open it, so make sure your inventory is clean and ready.

Vault rewards include region-exclusive loot, enhancement materials, and Primogems. The exact reward list has not been fully spelled out in official patch notes, but completionists will not want to skip it. This is the main payoff for all the cave diving and puzzle solving.

Timing and Banner Overlap

This phase arrived alongside active character and weapon banners. The overlap means your Primogem planning needs to account for both pulling and exploration.

There is always a risk of spending too much attention on exploration while a limited unit sits in the wish menu. If you are chasing a character, set a hard pulling limit before you start evermoon hunting. If you are low-spend or F2P, finish the event objectives first and then decide whether residual Primogems should go toward banners.

Squad Recommendations

Bring strong AoE and puzzle-proficient characters. Electro, Geo, and Anemo units with good crowd control or movement support make Hiisi Island's cave sections much easier. The Tsar fight especially rewards teams that can handle pressure while repositioning around arena mechanics.

How I Feel About the Randomization

I appreciate that HoYoverse is trying something new here. Non-linear reward structures and replayable chest routes give Hiisi Island more texture than a simple checklist zone. But there is a real frustration when critical progression depends on randomized seal drops.

Some players enjoy the flexibility. Others, myself included on a bad day, just want the third Evermoon Seal without revisiting every cave entrance. If future zones use this system, I hope HoYo adds some kind of pity mechanic or lets us track which unsolved chests are most likely to drop missing seals.

Final Planning Checklist

Before you attempt the Vault, run through this quickly:

• Finish both major questlines.

• Clear all puzzle and combat challenges tied to chest spawns.

• Check your inventory for three Evermoon Seals.

• Revisit any unfinished cave segment if you are short.

• Bring AoE, Geo, and Anemo utility for smoother clears.

• Save Primogems until you know whether you are pulling or just exploring.

The Hiisi Island Evermoon Seal and Treasure Vault cycle is a solid mix of story, combat, and puzzle design. It is not a race, but it does demand some planning. Unlock everything while the event is active, grab the Vault loot, and then relax before the next phase of the Nod-Krai saga arrives.