Unlock the door to Monstro Town’s darkest secret and face Culex, the legendary secret boss in Super Mario RPG-a formidable foe with roots in Final Fantasy lore and the toughest challenge in the game. To summon this interdimensional warrior, you’ll need to trade fireworks for a Shiny Stone and prepare for a battle that demands strategy, powerful gear, and nerves of steel. Defeating Culex not only tests your skills but rewards you with the game’s ultimate accessory, the Quartz Charm, making this hidden showdown a must for any true Mario RPG fan.
The secret boss from the original game, Culex, does indeed return for the Switch remake, and there’s another fight that’s even harder than him after that. We detail how to find Culex for the first time in Super Mario RPG, and how to take out the additional secret boss below.
[Ed. note: Spoilers for Super Mario RPG below.]
How to find Culex in Super Mario RPG
To find Culex in Super Mario RPG, you first need to obtain the Shiny Stone, which is key to unlocking the secret boss fight. Start by heading to Moleville and purchasing expensive Fireworks for 500 coins from a mole in the northwest house. Then, trade the Fireworks with a little mole girl hiding behind crates to receive the Shiny Stone. After acquiring the Shiny Stone, proceed to Monstro Town and locate the dark, sealed door near the weapon shop. Using the Shiny Stone on this door will unlock it, allowing you to enter and challenge Culex, one of the toughest optional bosses in the game.
To take on Culex, you need the Shiny Stone and access to Monstro Town. If you haven’t hit Monstro Town yet, just keep trucking in the game’s story until you get there.
You can get the Shiny Stone from a little girl in Moleville. She’ll trade it to you for a firework – which you can buy for 500 coins from a mole inside the building next to the little girl. The young mole girl can be hard to spot, but she’s behind these boxes here:
Once you get the Shiny Stone, head to the darker set of doors in the middle of Monstro Town. You can insert the Shiny Stone into the door and enter, though before you do, prepare for a pretty tough fight against Culex, the Final Fantasy-inspired boss.
We had no problem beating Culex after we cleared the game, but fighting him earlier may pose a challenge.
Once you beat Culex, you’ll get the Quartz Charm, an accessory that halves the damage you receive and adds 50% more damage to your own attacks.
Once you beat the Smithy and Culex, you’ll be able to take on another secret boss, as part of post game content.
How to find post-game Culex in Super Mario RPG
To find post-game Culex in Super Mario RPG, first complete the main story and defeat the final boss, Smithy. Then, obtain the Extra-Shiny Stone by defeating Duel-Ready Johnny in the post-game boss rematches. With the Extra-Shiny Stone in hand, return to Monstro Town and use it on the sealed door located near the Item Shop to unlock access to Culex’s rematch battle. This fight is considered the ultimate challenge in the game, requiring a well-leveled party and strategic preparation to overcome.
After beating Smithy and Culex the first time, you’ll actually be able to rematch a harder version of Culex. However, to do this, you have to clear out the post-game, which means you need to complete all the available rematches:
- Jinx (in the Monstro Town dojo)
- Booster (in Booster Tower)
- Punchinello (in the Mole Mines)
- Johnny (in the Sunken Ship)
- Belome (in Belome’s Temple)
- Bundt (in the Marrymore chapel)
Along the way, you’ll get rewards like a weapon for Bowser or accessories that’ll make the other fights easier. Johnny specifically rewards you with the Extra-Shiny Stone, which you’ll need to open the door to Culex for this extra fight. However, Culex’s door in Monstro Town will not be there until you complete all rematches against the baddies above, based on our playthrough at least.
These fights are all tough and have new gimmicks added on top of the original fight, so don’t be surprised if it takes you a few tries to get through.
Once you actually get to the second Culex battle, prepare for the fight of your life. He’s significantly harder and beefier than the original Culex fight, so if you’ve been holding on to items like Rock Candy or Red Essence, now is the time to use them.
This version of Culex rewarded us with a key item that we haven’t quite figured out the use for. He also does count the number of turns it takes to beat him, so there’s no doubt that many experienced players will be racing to see who can take him down the fastest.
What hidden steps lead to the elusive Super Mario RPG secret boss
To unlock the elusive secret boss Culex in Super Mario RPG, follow these hidden steps:
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After progressing to Monstro Town late in the game, you will notice a mysterious locked black door that cannot be opened by normal means.
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Head back to Moleville and go north to a house where a mole sells Fireworks for 500 coins each.
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Purchase Fireworks from this mole, then exit the house and look for a small mole girl wearing a pink bow hiding behind crates nearby. She will trade you a Shiny Stone in exchange for the Fireworks.
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The Shiny Stone is the key to unlocking the black door in Monstro Town. Return there and use the Shiny Stone to open the door and access the secret boss fight with Culex.
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Be prepared: Culex is a very tough boss, recommended for players at level 20 or higher with strong equipment like the Lazy Shell armor to increase defense.
This sequence of trading fireworks for a Shiny Stone and unlocking the hidden door reveals one of the most challenging and iconic secret battles in Super Mario RPG.
What items do I need to unlock the secret boss in Monstro Town
To unlock the secret boss Culex in Monstro Town in Super Mario RPG, you need the following items:
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Shiny Stone: This is the key item required to open the sealed black door in Monstro Town where Culex awaits.
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Fireworks: You must first buy Fireworks from a mole in Moleville (costing 500 coins each) and then trade them with a small mole girl wearing a pink bow near the mole’s house to receive the Shiny Stone.
Once you have the Shiny Stone, return to Monstro Town and use it to unlock the black door and access the secret boss fight with Culex.
