Hello! This is my first time participating in the fall festival, and I want to try to brew a Sylesti, but it says I need Catalysts to begin or something like that. Can anyone tell me where I can find them?

Thanks!

You can find Catalysts in the Festival shop for 300 chocolate coins. Going to Explore/Seasonal Festival/Task List will show you what kind of things you can do to earn those coins. The one in the Festival shop is called 'Regular Brew Catalyst', there's also a version that's 'Premium Brew Catalyst' that will give you a higher chance of getting a rarer pet.

If you like Aurleons and already have the 5k gold you need for your broth, I have a catalyst I can give you. :)

They can also sometimes be found after defeating a boss.

they can also be obtained in the zone randomly rarely from chests/pumpkins/whatever and drop from non-boss enemies (not sure if they drop from wild sylesti, I do not pay enough attention to what I've just mauled to remember)