Super Mario RPG: How To Find & Defeat The Culex

Super Mario RPG: Legend of the Seven Stars has an infamous secret boss that you can only fight if you have a special item on you.

This encounter requires an extremely precise strategy to best if you want to squeak out a victory, and it's easily the toughest fight in the original game and one of the hardest fights in the remake.

In this guide, we'll show you where to find this secret boss, how to unlock it, and how to defeat it. This guide will work for both the SNES and the Switch versions of the game.

Super Mario RPG: How To Find & Defeat Culex

Where to find the Culex

The secret boss can be found in Monstro Town behind a grey-coloured door. You'll find this next to the Item Shop and the Three Musty Fears' house.

However, you won't be able to enter the door without a special item.

How to unlock Culex

To unlock the secret boss, you will need to have the Shiny Stone on you. And to get that, you'll need to have a little bit of money spare.

Where to find the Shiny Stone

You can find the Shiny Stone in Moleville, and you can get this right after finishing the Mole Mines if you want to. All you need is 500 coins.

In Moleville, a young mole is hiding behind some crates on the second level of town. Talk to her and you'll find out she wants some fireworks and will give you a Shiny Stone in return.

The fireworks are close by. Just head to the hose to the left of the mole. Once inside, talk to the mole wearing the green overalls at the back of the house. He's selling fireworks for 500 coins right now — buy them from him if you have the money to spare.

Then, head back outside and talk to the little mole to swap the fireworks for your Shiny Stone. Now you can get in the door in Monstro Town.

How to prepare for Culex

Before you think about challenging the secret boss, there are a few things we would highly recommend you get.

First of all, get the Lazy Shell weapon for Mario and the Lazy Shell armour for anyone else — preferably Peach. The armour is actually the more important aspect, here — damage is good and all, but the Lazy Shell armour will boost Peach's defense greatly, ensuring she survives basically every single attack. If you don't have these items, check out our guide on How To Get The Lazy Shell.

Second, stock up on Maple Syrup and Royal Syrup. You'll want to make sure you always have Flower Points so Peach can heal, and these are the best two items to heal up with. Kerokero cola/Croakacola is also useful because it heals both health and Flower Points: good in a pinch, then. These are less common and you can only grab them if you have lots of Frog Coins, have been searching for all of the Hidden Treasures, or recited all Melody Bay songs.

Next, use your best accessories here — we gave Mario the Zoom Shoes to ensure he had extra speed, Geno was wearing the Jinx Belt to boost all of his stats, while Peach wore the Safety Ring to protect her against status effects. If you don't have the Jinx Belt, head on over to our guide on How To Defeat Jinx.

Lastly, we recommend being at least level 20 before taking on Culex. We beat this tough boss at level 24.

How to beat Culex

Recommended party: Mario, Geno, Peach

Surprise! It's Culex and his four crystals. This is an extremely tough fight that you have to prepare in advance for, and if you follow our tips above, you should be ready.

You want to take out as many crystals as you can before taking out Culex — we'd recommend two at least. Each crystal represents a different element — Red is fire, blue is water (ice), Yellow is earth, and green is wind (lightning). That means you have four different elemental attacks going at you and Culex. Five attacks per round? Ouch. That also basically rules out any multi-target elemental spells, so Mallow (unless it's Star Rain) is sort of useless, here.

You'll be hit by a barrage of spells. Culex will start the fight with Meteor Storm, but you'll see all sorts in this fight, from Petal Storm, Dark Star, Flare, Diamond Saw, and more. As with most multi-target spells, you won't be able to block the damage from them, so when you do see a rare Diamond Saw or electric attack, try to block it to reduce the amount of damage you take. Mario and Geno should focus on taking out the crystals. Don't waste a turn using Geno Boost on a character, as Culex can use Shredder, an attack that removes all positive status effects.

Because you're taking so much damage every single round, Peach is here purely for healing purposes. The Lazy Shell will ensure the damage she takes is minimised while allowing her to use her low-cost healing spells every single turn. Group Hug heals the whole party and removes status effects, while only costing 4 FP. If any characters are knocked out, use Peach's revive spell or a Pick Me Up.

You can use multi-hit attacks like Ultra Jump or Geno Flash to damage everything on the screen slightly, but we recommend just using your standard physical attacks on the individual crystals. Plus, in the Switch remake, the splash damage from a perfectly timed hit will be extremely useful.

The other thing you can do with Mario, Geno, and Peach is use their Triple Move, which makes the party invulnerable to a single attack. If you're panicking or low on health, give it a shot. Eventually, the crystals — and even Culex — might run out of FP, meaning they won't be able to use magic on you.

Once you've taken down one crystal, things get a little easier. We took out the Fire Crystal and then the Water Crystal. With two crystals gone, focus all of your might on Culex — but keep Peach on healing duty, because the remaining foes can do a lot of damage.

If Culex dies before the remaining crystals, then you don't need to worry about taking them out, afterwards — you win automatically. Congrats!

What do you get for defeating Culex?

Culex will admit defeat and hand over the Quartz Charm, an extremely powerful accessory that halves the damage you take from enemies and doubles your own damage.

Not only that, it also protects the wearer against one-hit KOs. Well worth getting, particularly in the Switch remake, where more challenges await once you've rolled the credits...

Can you fight Culex again?

In the SNES version, once you've defeated Culex, that's it — you passed the hardest challenge the game has to offer. Congrats! He'll vanish and the door in Monstro Town will also disappear.

In the Switch remake, he'll also vanish, but if you pursue the post-game bosses, you might be in for a surprise. Check out our post-game guide for Super Mario RPG, including how to defeat the hardest boss in the game.

For more help on getting through Super Mario RPG, check out our full Super Mario RPG guide for everything you need.