I am replying long after you made this thread. I just saw it today!
I found an image of a sword and some fire that would fit well together if you used layered them. Perhaps you could use photoshop. I tried to, but the site I was using wouldn’t let me combine the images.
Unfortunately the sword is not even close to what you had asked for. I couldn’t find a sword like the one you wanted.
I was able to use photoshop to make the sword gold.
Here is the original in case you’d prefer that.
The fire is nice and straight so it would fit on the sword if you could rotate it.
If you’re using the classic animation, I don’t know how to help because there aren’t any good animations for swordfighting.
For INK, you could have them hold the sword in the holding baseball bat animation, and just put the overlay on their hands. They move back and forth, which makes it a little harder. You can estimate where their hands move to in each direction, and move the sword to that spot and estimate how long you think it takes for their hands to move there, and program it into the overlay movement, and test it. If you have iMovie and are previewing on a tablet, you can make a screen recording of the character’s and the sword’s movements, perhaps while zoomed in on their hands, and put the screen recording in slow motion. Change the speed of the overlay accordingly, and keep testing it and changing it as many times as you need to get it right. Another animation you should definitely use would be the punching animation. You can do the same thing, but also make sure it hits where you want it to hit. Another animation that could work for slicing could be the frustrated animation.
For limelight, the same things apply, but their movements are different. They have more holding baseball bat animations, the punch animation is slower, but they also have the pitchfork animation.