Fire is more about colour than shape
Photoshop has a great Fill layer type that remaps value to a customisable gradient, and quickly makes fire effects. Start with a group and set it to Screen. On the bottom, create a black layer and an empty layer for painting on. Then create a Gradient Map layer and adjust the gradient to fall through the effect’s colours. Finally, paint with white in the empty layer.
I want to show that the Witch Queen no longer has true physicality of her own. It’s more believable if there’s nothing vulnerable to chop or stab. I also want to impart a visual connection and some extra threat to the Morgul blade. Flat black, but surging with energy, melting the scabbard it’s being drawn from. Seems dangerous to me.