One of the best ways of getting more powerful fast in Clair Obscur Expedition 33 is to upgrade each of the weapons of your party members. Weapon upgrades let you do significantly more damage to the enemies, allowing you to have a much easier time progressing through some of the harder challenges.
However, the system is a bit complicated, and you will not have access to weapon upgrades from the get-go. There are a few nuances to the system as well, and if you are looking to learn everything there is about it in the RPG, then the guide below will help you out.
How to unlock Weapon Upgrades in Clair Obscur Expedition 33

The weapon upgrade system is not something that you will have access to right away in Clair Obscur Expedition 33. You will need to progress the story a fair bit and meet the Curator to be able to use the system.
This happens after you have completed around 3-to-4 hours of the narrative, where Maelle will eventually join you and then introduce you to the Curator.
After that, you will then complete The Flying Waters area with the trio and then make your way to a camp. Here, a cutscene will play, and you will get to upgrade your weapons by interacting with the Curator.
When you speak to him, you will get a small tutorial about how the weapon upgrade system works.
How do Weapon Upgrades work in Clair Obscur Expedition 33
Here are some of the key features that you might want to keep in mind when it comes to Weapon Upgrades in Clair Obscur Expedition 33:
1) Weapon upgrades can, at times, unlock passive effects
When upgrading weapons, if you are able to improve them enough, you will be able to unlock certain passive effects for them. However, these effects are weapon exclusive and cannot be equipped on your character like you would with Lumina.
2) Different weapons have different scaling
Different weapons come with different attributes that they scale with. So keep this little feature in mind when upgrading weapons. You will not want to unnecessarily waste resources on armaments that you are not going to need.
3) Chroma Catalysts are needed for weapon upgrades
Chroma Catalysts are the main resource that you need to get your weapon upgrades going in Clair Obscur Expedition 33. You will be able to farm this item by exploring the map and taking down enemies to obtain it as a drop.
4) Getting the same weapon twice will let you upgrade it
There will be moments when you find a duplicate of a weapon that you have already collected before. When that happens, you will be receiving a significant boost to the one that you already have.
5) The Curator will help you upgrade Lumina as well
Apart from weapons, the Curator will help you upgrade your Lumina as well in Clair Obscur Expedition 33. With more upgrades, you will then be able to equip more Pictos on your party members.

6) Rest Points can let you upgrade your weapon during the end game
As you get to some of the final chapters in Clair Obscur Expedition 33, you will unlock the feature that lets you upgrade weapons and Lumina fem the Rest Points itself. You will not be requiring the Curator for this, and it is a neat little feature to have.
Note: Once you have upgraded your first weapon in Clair Obscur Expedition 33, you will automatically unlock the ‘Weapon Upgrade’ trophy/achievement.