From the source description:  
I started this shortly after EqG came out, but I forgot about/got tired of it. It’s now a bit outdated since my headcanon has changed.
 
First it the Alpha demons. They are born demons and live in Tartarus under the command of their King:  
 
They have powerful magic and can mask themselves like the changelings.  
They can change normal ponies into Beta demons over a long period of time. Example: Flash is an Alpha who escaped from (human world) Tartarus and changed Shimmer. (crazy theories ftw!) He planned to change Twilight too, but now that’s pony-Flash’s job.
 
Second are the Beta demons. They are changed by Alphas and require a magic source to transform (such as an element of harmony, hint hint). They can temporarily change normal ponies into Gamma demons. Their magic powers depend on their source. They can’t control their transformation.
 
Last are the Gamma demons. They can’t change others anymore, and can’t transform by themselves. They need either a Beta or an Alpha to change them. They don’t have magic.
 
I thought of this to come up with a backstory for Flash, since he was so bland- kind of like Sombra. Now I have a better idea, though.

Snips is the Omega.

Damn, Flash looks badass!

I should probably do my version of the demon forms of SS and SnS…

Alright. :3