All of them except the top middle are villains
 
The first one’s name is Loveless Serenade (suggested by Fandom-Crockpot)) She is similar to a siren, she lives on the top of a mountain, she flies down at times and uses her voice to make ponies fall in love with her. Her voice hypnotizes ponies and they follow her up the mountain where she feeds off their energy to become stronger. She does eventually release them, but the have to find their way back down the mountain by themselves, rarely does any pony make it. The pegasi and unicorns she release have been drained of energy to the point where they can’t fly or do magic so they have to make it down the mountain by hoof. Her form is just an illusion, I haven’t designed her true form yet
 
The top middle is a unicorn from ancient times who is sent forward in time to the present, I haven’t really worked out all the details.
 
The third one is an earth pony who can sometimes predict to future, she uses for her own gain, and eventually joins up with some villains.
 
The bottom left is a powerful “unicorn” from long ago who wanted to rule equestria (i haven’t really worked out much of his backstory yet) but he lived in a frozen land in the north, he was eventually sealed away in ice, not sure by who yet, but he is later freed in the present by the bat pony
 
The bottom middle is an earth pony who studies magic and is experimenting with ways for an earth pony like himself to use magic. He is jealous of unicorns and pegasi and desires power.
 
The last on is a bat pony who was once served Luna, he becomes jealous of the princess’s power, he wants to overthrow her and rule the night. He learns of the unicorn (bottom left) from long ago who is still frozen in ice, he frees him and tells him he will help him take over equestria, and recruit some others to help as long as he can rule the night. So all the ponies in this picture (except for top middle) join together