Original Source: Technical Artist Bootcamp: The VFX Of Diablo, GDC 2013
BlendAdd is a method to saturate a material while retaining the glow. With add blending (no alpha), eventually your render layers will equal white, blowing out the image. With a simple blend using an opacity alpha, you end up having great saturation but lose the glow effect. By combining both of these methods you end up with the Blend-Add on the right. - GDC 2013
$$ (TEX1 * TEX2 * 2) * infinity = Dynamic Alpha Shapes $$
Looks better if you scale one texture by 0.5. Get Clouds.
Adding another texture with a different speed gives you even more complexity.
Add another texture and have it be a mask.
What happens when you have 7 particles that are offset and randomized in speed. High complexity.d
What happens when you combine colors?
Add particle rotation and scale and opacity fade over time.
RGBA channels are all being multiplied together. Has low overdraw.