To get the Monstrous Cusk in Fisch, unlock The Deep and the Gloomy Crevice, bring a Harpoon Gun during an active Monstrous Cusk hunt, damage the boss by shooting its head as it moves from the Gloomy Crevice toward Deep City, then finish the slowed catching minigame while ignoring the purple circles.
The Monstrous Cusk is one of the tougher catches in The Deep — not a fish you reel in, but a harpoon boss you damage, chase, and finally land through a special catching minigame. It arrived with the Deep Update and lives in the Gloomy Crevice, and pulling a single Tooth from it is the first real step toward the late-game Cusk Purger rod. Here’s the full route, from prepping your gear to finishing the slowed catch.
Monstrous Cusk requirements checklist
| Requirement | Details |
|---|---|
| Access to The Deep | Clear the Deep questline from Castaway Cliffs to reach Deep City and the Gloomy Crevice. |
| Deep Survey Device MK II | Its Light Module is the only reliable way to see inside the pitch-dark Gloomy Crevice. |
| Harpoon Gun | The Monstrous Cusk is a harpoon boss and cannot be caught with a normal fishing rod. |
| Active Monstrous Cusk hunt | The boss must be awakened before it appears in the Crevice. |
Landing the Monstrous Cusk isn’t a normal cast-and-reel catch — it’s a harpoon boss you chase down inside The Deep. Before you can even see it, you need access to that zone: sail to Castaway Cliffs, pass through the hidden barrier to board The Deep ship, talk to Cadet Shimmerfin for the Deep Survey Device, then repair it down in Deep City. From there, restore the sector beacons with Chief Engineer Nereus to upgrade to MK II — the version with the Light Module you’ll rely on to see anything in the Gloomy Crevice. Here’s the short list before you head down.
Reaching the Gloomy Crevice in Fisch
Once the hunt is live and your gear is ready, dropping into the Gloomy Crevice takes only a quick dive from The Deep’s main area.
Head into The Deep
Travel to The Deep and move toward the nearest building in the main area.
Dive straight down at the building
Drop straight down directly in front of that main building.
Land in the Gloomy Crevice
The dive drops you into the Gloomy Crevice, the dark sub-zone where the hunt plays out.
Video help
Awakening the Monstrous Cusk hunt
You can only catch the Monstrous Cusk while its hunt is active, and the boss doesn’t just spawn on a timer once you arrive. The hunt is triggered by Faceless Cusk in the Gloomy Crevice — you do not need to catch Faceless Cusk to awaken the Monstrous Cusk boss.
Since you aren’t grinding a fixed number of Faceless Cusk catches to trigger it, plan around the hunt becoming active rather than counting on a set catch total. It’s also worth holding onto any Faceless Cusks you already have — you’ll want them later rather than selling them off early.
How to catch the Monstrous Cusk in Fisch
This is the full pursuit — spot the boss, wear it down with head shots, chase it toward Deep City, and land the slowed catch at the end.
- Spot the Monstrous Cusk — Look around the Gloomy Crevice for the Monstrous Cusk swimming through the area.
- Equip the Harpoon Gun and hit its head — Pull out your Harpoon Gun and land repeated shots directly on the boss’s head.
- Chase it toward Deep City — After enough damage it leaves the Crevice and swims toward the Deep City POI, so follow it out.
- Keep landing head shots in the new area — Stay on the creature and keep hitting its head, using flank shots to slow it if it starts pulling away.
- Trigger the special catching minigame — Maintain constant pressure until the special catching minigame finally appears.
- Work through the slowed catch — Your progress speed drops by 90%, so hold steady and let the bar fill far slower than a normal catch.
- Leave the purple circles alone — Do not tap or click the purple circles that pop up — just keep the catch going.
- Land the Monstrous Cusk — Finish the minigame to add the Monstrous Cusk to your catches and claim your Tooth.
Never ease off the head shots during the Deep City chase — if you let the boss recover ground it can reach Deep City and the hunt fails before the catching minigame ever starts.
Surviving the slowed catching minigame
The catching minigame is deliberately punishing. Because your progress speed is cut by 90%, the catch drags on far longer than anything you’ve reeled in before, and the instinct to hurry it along by mashing prompts is exactly what causes misses — steady, controlled input fills the bar, panic doesn’t. The purple circles that appear mid-catch exist to bait that panic, so treat them as something to actively avoid rather than another prompt to hit.
Beyond the minigame itself, most failed runs come down to a few avoidable errors: bringing only a rod instead of a Harpoon Gun, entering the Gloomy Crevice on the outdated MK I device and fishing blind, and letting up on the head shots during the pursuit so the boss escapes before the catch phase ever begins.
Cusk Tooth rewards and the Cusk Purger rod
| Item | Use |
|---|---|
| Monstrous Cusk Tooth | One per hunt; 3 needed for the Cusk Purger rod. |
| Abyssal Biofluid | Cusk Purger crafting material. |
| Radiant Prism Scales | Cusk Purger material; also used in Deep quest lines. |
| Hardened Chitin | Cusk Purger crafting material. |
| Refined Scrap | Cusk Purger crafting material. |
| Ancient Bones | Cusk Purger crafting material. |
| Line of the Deep | Cusk Purger component earned from the Cartographer quest. |
| 750,000 C$ | Currency cost to craft the Cusk Purger. |
Every successful hunt drops one Monstrous Cusk Tooth, and the reason to farm the boss is the Cusk Purger — a late-game rod you craft at the Crafting Anvil inside the Ancient Archives. You need 3× Monstrous Cusk Tooth for it, which means at least three clean hunts, alongside a stack of other Deep materials. Keep your Faceless Cusks and Radiant Prism Scales while you farm, too — offloading them early leaves you short for the Cartographer quest and the Line of the Deep the rod also demands.
Related Fisch guides
Frequently Asked Questions
Can you catch the Monstrous Cusk with a normal fishing rod?
No. It’s a harpoon boss, so you need a Harpoon Gun to damage and chase it — a standard rod can’t start or carry the fight. The only fishing-style step is the slowed catching minigame at the very end, and you only reach that after wearing the boss down with harpoon shots.
Do you need the Deep Survey Device MK II for the Gloomy Crevice?
Yes. The MK II Light Module is what actually lets you see inside the pitch-dark Crevice. Older advice that says you can enter on MK I no longer holds — go in on MK I and you’ll be effectively blind and unable to track the boss.
What should you do with the purple circles in the Monstrous Cusk minigame?
Ignore them completely. Don’t tap or click the purple circles when they appear during the slowed catch — interacting with them works against you. Just keep the normal catch going and let the bar fill.
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