I'll say it's pretty easy compared to other puzzles game has to offer. There are some domains where you have to complete their respective puzzles in phases and require quite a bit of time to complete. Sure, you can complete them in a breeze if you have a walkthrough to refer to or see a tutorial on youtube video. Coming to Crimson witch of flames' domain, this domain is pretty simple to unlock, and all you have to do is light up torches. Pyro torches are generally located in different directions. After lighting them up, you can apply the Geo element on the totem to unlock the domain. Even if we talk about nearby enemies, they are not tough to deal with because they are general mobs you see in the overworld. Mitachurls, hilichurls and Cicin mages are the common enemies you will encounter throughout your journey. By the time you reach this domain, you will already have good invested characters to fight them. So, I'll recommend you invest in your characters and take things slow to clear the content.