Yo! Some buddies were asking about the practical application of this trail. I wanted to show an example of how I used this exact trail in League of Legends 
This is Kayn, he’s a shadow assassin that battles for control over a powerful possessed weapon. He transforms halfway through the game depending on who wins, Kayn, or the weapon Rhaast! Kayn has the power to walk through walls:
Maybe you already recognize the trail
Here it is in isolation:
I have one trail (like the above scrolling ones) that is being multiplied by itself scrolling at a slower rate (the red trail in the gif above) To give it that shadowy, inky dissolve I have an alpha erosion over the emitters lifetime:
Here is the trail WITHOUT the mult, just the alpha erosion or hue
You can get some really cool stuff with erosion That’s also what I used on Kayn’s body. If you have any questions let me know 