Queen Azalea ref

A new Villainous Queenie has left her mark on Equestria.

Azalea is a toxic Changeling who uses her vast abilities over poisons to weaken her prey, corrupting them and ultimately either transforming them into one of her servants or simply discarding them. 
She hates ponies, seeing them as an illness that had stolen her kinds place and she will one day try to change that by over-throwing the Princesses and ruling all of Equestria with a vast army of Changelings.