Fishing in Mina the Hollower is much more than a side activity. Players who fully commit to filling their fish collection will eventually uncover Thalassion, a giant aquatic monster hidden behind one of the game’s longest optional questlines. While not required for story progression, this encounter serves as the climax of the fishing quest and offers one of the most unique secret boss battles in the game.
| Category | Details |
|---|---|
| Boss Name | Thalassion |
| Type | Secret Boss |
| Location | Fishing Hole, Backwaters |
| Quest Requirement | Catch all fish except the final Backwaters fish |
| Recommended Equipment | Fishing Rod, Drill Driver or Raft |
| Reward | Gilded Rod |
| Difficulty | Moderate to High |
| Optional | Yes |
Where to find Thalassion
Thalassion is located in the Fishing Hole area of Backwaters. To unlock the encounter, you must first obtain the Fishing Rod from the fishermen Irwin and Durwin, then catch all 15 fish available in every region of the game while leaving one remaining fish uncaught in Backwaters. Once the collection requirements are met, return to their fishing camp to access the hidden path leading to the boss.
How to reach the Thalassion boss in Mina the Hollower
Obtain the Fishing Rod from Irwin and Durwin and begin filling out your fish collection. Catch all 15 fish found in every major area of the game.
Leave the final remaining fish in Backwaters uncaught. Return to the fishing camp in Backwaters.
Equip the Fishing Rod and either the Drill Driver or use the raft to access the route beyond the camp.
Travel to the southeast section of the area and use the Fishing Rod on the hanging slime above to pull yourself across the gap. Continue through the next screen to reach Thalassion’s arena and initiate the battle.
What the Thalassion fight is like
Unlike many bosses that occupy large arenas, Thalassion forces you to fight in a confined water-based battlefield. The giant fish spends much of the encounter swimming around the arena before launching aggressive attacks.
Its most dangerous moves include rushing forward with a charging bite attack and sending waves across the arena. Because space is limited, mistimed dodges can quickly lead to heavy damage. The boss hits surprisingly hard, making patience more important than aggression.
How to beat Thalassion
Focus on survival during the opening moments and learn the timing of its charges.
Avoid overcommitting to attacks. The small arena leaves little room for recovery if you get caught. Watch for moments when Thalassion dives or exposes its vulnerable tail section.
Land a few safe hits and immediately reposition. Use burrowing and movement abilities to avoid incoming waves and bites.
Repeat the pattern patiently until the boss is defeated.
It is recommended to have a defensive approach, as attempting long attack strings often results in getting hit by the boss’s high-damage attacks.
Thalassion boss drops and rewards
| Reward | Description |
|---|---|
| Gilded Rod | Final Fishing Rod |
| Thalassion Pearl | Thalassion Boss drop |
| Fishing Reactor feat/achievement | Obtained after speaking with the fishing NPCs following the fight |
| Secret Boss Defeat | Counts as one of the game’s optional secret bosses |
After defeating Thalassion, return to Irwin and Durwin. Speaking with them awards the final fish-related collectible and ultimately grants the Gilded Rod, completing the fishing progression path.
Tips for an easier victory
| Tip | Benefit |
|---|---|
| Bring healing resources | Provides more room for mistakes |
| Stay patient | Prevents unnecessary damage |
| Attack only after safe openings | Reduces risk in the small arena |
| Equip mobility tools | Helps avoid charges and waves |
| Learn attack timing first | Makes the encounter significantly easier |
Thalassion stands out because it transforms a peaceful collection activity into a challenging secret boss encounter. The lengthy requirement of catching nearly every fish in the game makes this one of Mina the Hollower’s most involved optional challenges, and the Gilded Rod serves as a fitting reward for players who fully explore the fishing system.
For completionists, Thalassion is one of the most important secret bosses in Mina the Hollower. While reaching the encounter requires substantial fishing progress, the battle itself is memorable, rewarding, and ultimately necessary for finishing the game’s fishing collection. If you’re aiming for 100% completion, this giant aquatic beast should definitely be on your checklist.
