Major spoiler warning: This guide names optional bosses, locations, unlock conditions, quest steps, rewards, and late-game content.
Verification note: This page combines current boss-list, boss-order, community-wiki, and published guide information. Conflicting route labels are kept general until the exact in-game wording can be confirmed.

Quick Answer: How Many Secret Bosses Are There?

There are nine commonly documented secret bosses. Nether Kraken is listed separately because it is an optional, missable encounter during the opening ship sequence.

These encounters are not unlocked in one consistent way. Some require side quests, some appear only after a story milestone, and others are hidden behind Plasma Vial doors, Spark-slot doors, traversal routes, or collection progress.

9 Secret bosses
1 Optional intro boss
10 Cleanup encounters

All Secret and Optional Bosses

01

Queensbury Crypt

Midden

Dialogue Trigger

Midden is found in the Ancestral Chamber in Queensbury Crypt, behind a door that requires two Plasma Vials. The encounter begins after choosing the insulting dialogue response.

Location Queensbury Crypt — Ancestral Chamber.
Condition Open the two-Vial door and insult Midden.
Reward Fly Bait Trinket.
02

Ossex Ambush

Maxi

Story Timing

Maxi ambushes Mina when she returns to Ossex through the eastern or right-side entrance after completing Queensbury Crypt.

Location Ossex eastern entrance.
Condition Return to Ossex after clearing Queensbury Crypt.
Reward Trinket Bag and an additional equip slot.
03

Blacksmith Shop Encounter

Armand

Shop Trigger

Armand is connected to Legovich's Arms in Ossex. After buying from Legovich, attempt to purchase a second item. The resulting shop event leads to the hidden encounter below.

Location Legovich's Arms in Ossex.
Condition Attempt to buy a second item and follow the shop event.
Reward Legovich's normal shop inventory is restored.
04

Ack & Dak Quest

The Dugin

Randomized Spawn

The Dugin quest starts with Ack and Dak on Ossex High Street after Queensbury Crypt. The encounter can appear in either Southern Outskirts or Western Wilds and must be completed twice.

Location Southern Outskirts or Western Wilds.
Condition Speak with Ack and Dak, then defeat Dugin twice.
Reward Lace Glove Trinket.
Spawn note: The encounter chance is randomized. Leaving and re-entering the relevant room can produce another chance for it to appear.
05

Bayou Band Quest

Wonder Willis

Long Quest Chain

Wonder Willis is the final payoff to the Bayou Band quest. Rescue the frog in Backwaters, reunite it with the band, fund their journey to Ossex, and enter the Music Hall.

Location Music Hall in Ossex — Bowery.
Condition Rescue the frog, reunite the band, pay 100 Bones, then burrow beneath the crowd.
Reward Pneumatic Armlet Trinket.
Quest reward: Reuniting the frog with the band also awards Tumbling Tutu before the Willis fight becomes available.
06

Windy Generator

Dark Deluxy

Spark Containers

Dark Deluxy is hidden behind a door near the Windy Generator that requires two Spark Containers. Open the route and escort Luxy back to the Generator to trigger the fight.

Location Windy Generator route.
Condition Carry two Spark Containers and escort Luxy back.
Reward Spark Container after healing Dark Deluxy.
Important: Keep one spare Plasma Vial. The reward is received by healing Dark Deluxy after the fight.
07

Coltrane Peak

Mirren

Hidden Ice Route

Mirren is found near an abandoned carriage in Frostbite Woods. Her route is reached by digging beneath the ice from the Underlab. Offering to help her triggers the hostile encounter.

Location Coltrane Peak — Frostbite Woods.
Condition Dig under the ice from the Underlab and offer help.
Reward Blinking Glass Trinket.
08

Goddred's Grave

Evra the Undying

Traversal Route

Evra is found inside Goddred's Grave, a hidden mini-dungeon reached through the eastern side of the Courtyard route. Strong traversal tools are needed to cross the gap and reach the gate.

Location Goddred's Grave.
Condition Reach the eastern Courtyard route, cross the gap, and open the three-Vial gate.
Reward Health Rose and one permanent HP segment.
Preparation: Drill Driver is a commonly recommended traversal tool for reaching this hidden route.
09

Late Fishing Quest

Thalassion

Super-Boss

Thalassion appears at the Backwaters Fishing Hole late in the fishing quest chain. Treat this as optional endgame content rather than a normal regional progression fight.

Location Backwaters — Fishing Hole.
Condition Advance the fishing quest chain to its late stage.
Reward Gilded Rod fishing upgrade.

There is no single mandatory order for all optional bosses. The most practical approach is to complete each encounter when its location or quest chain naturally becomes available.

  1. Nether Kraken during the prologue
  2. Midden while exploring Queensbury Crypt
  3. Maxi when returning to Ossex after Queensbury
  4. Armand through Legovich's Arms
  5. The Dugin through Ack and Dak
  6. Wonder Willis after the Bayou Band quest
  7. Dark Deluxy near the Windy Generator
  8. Mirren during Coltrane Peak cleanup
  9. Evra after obtaining strong traversal tools
  10. Thalassion during late-game fishing cleanup

What to Bring Before Hunting Secret Bosses

  • Bank spare Bones before entering unfamiliar optional routes.
  • Carry Plasma Vials for Midden, Evra, and Dark Deluxy's reward condition.
  • Keep traversal Sidearms available for hidden entrances.
  • Use survival Trinkets while learning unfamiliar encounters.
  • Check each reward or post-fight interaction before leaving the room.

Are Any Secret Bosses Permanently Missable?

Nether Kraken is the clearest missable encounter because it occurs during the opening sequence. Later secret bosses are generally tied to quests, hidden routes, NPC triggers, or special doors that should be checked before starting a new playthrough.

For final completion, review this list together with the Boss Database, Hidden Secrets archive, Trinket checklist, and 100% Cleanup Guide.

Continue Exploring

Hidden Secrets Archive Hidden endings, transformations, easter eggs, mysteries, and unusual interactions. Boss Difficulty Ratings Compare major, optional, and secret bosses on the five-star difficulty scale. Complete Walkthrough Follow the main route and see where optional encounters fit into progression. Boss Database Browse major, optional, secret, and special boss encounters. Best Builds Prepare survival, damage, counter, and cleanup loadouts. 100% Cleanup Checklist Check bosses, Trinkets, collectibles, secrets, and completion tasks.

Guide details were cross-checked against current boss databases, community wiki entries, boss-order notes, and published walkthrough coverage. Unclear route labels are intentionally kept general rather than presented as confirmed in-game wording.