quick tutorial on how I draw flames
(left: gale dekarios from bg3, right: my friend kay's elder scrolls online character, vanta)
(note: I draw in photoshop, but this will probably work in other drawing programs with similar setups)
if you're doing something similar and drawing a spellcaster casting fireballs, the first step I'd recommend is doing a dynamic pose. I used a dynamic photo of prince for the drawing on the left, and a martial arts pose from trueref (who have tons and tons of free pose packs and have a no-ai policy) on the right. I've also seen some gale fanartists say they use photos of orchestral conductors as reference for spellcasters.
if you're using red fire, you can use photo ref, but if it's green/blue/purple/whatever, just wing it. (fuck it, it's magic.)
draw the flames on a separate layer than the rest of the lineart, and if you use black lines like I do, don't use them for the flames (so they look less solid). remember to vary the direction of the flames, and periodically add little flickers coming off of it. (if you're drawing a spellcaster, have it go in the direction they're casting.) the inner flames shouldn't follow the same directions. remember, things like flames, leaves, grass, etc. are never consistent or 'perfect' in nature.
duplicate this layer and use an overlay filter like 'hard light' on it
use an 'outer glow' in the same color scheme as the flames
fiddle with the hard light and outer glow so it's not at 100%, things sometimes look more 'natural' when the opacity isn't as intense
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bonus: how to do the 'aura' in the second image:
1. soft round brush in the same color as the flames, fiddle with things like spacing, brightness, amount jitter, etc. to your liking (I have all the settings set to pressure sensitive because I do this on my tablet)
2. apply on a new layer where you'd like, remember you can undo it if it doesn't come out as you want, for the vanta image I had it as a 'halo' outline and then lowered the opacity so it again, wasn't as intense