Transition from fire to smoke to nothing?

I’m trying to make a magical mask appear from a fireball, but I’m struggling with how to transition from the fireball into the mask and make it look good. One domain is animated into frame and then the smoke mixes with the fire from the ball and you get a nice flamey smoke effect but how do I get rid of the flaming ball, I tried to animate the fire away in about 5 frames but it doesn’t seem to work very well because it’s one domain inside another and there might be some conflict, I don’t know. So I animated the domain up into the sky hoping that it would fade away smoothly, but as you can see in the image, the fireball remains and it overall looks kind of crappy when it shoots out.

Any idea how I can make the fireball dissappear smoothly from the scene?

Have you tried moving the fireball backwards on the z axis so that it disappears that way? Maybe a mixture of up and back?
I’m a bit of a blender n00b so sorry if this doesn’t help.

What about animating scale of the fire emitter and then density for the fire?