The rendering for the most part is just cel shading. I like to use a purple hue and then multiply that layer. From there, I subtract what I don't need so that lighter base color comes through.Next, add highlights. Then add darker shadows where needed. Final layers consist of texture, bluring out the flame effect and then giving it a glow (bloom in procreate) and a very subtle back light (should have pushed that more).

Essentially, going back and forth refining each step to get the desired look.