Evil/ Nightmare moon/ wicked mare version of Princess Twilight Sparkle
as you remember I drew "Princess of uniting" and since "too much of uniting and friendship" becomes into enslaving others. BEHOLD QUEEN OF SLAVES!!
beside her you see her own sword, I drew swords for royal sisters too (you can see them in my gallery @princesses vs dragons series). Twilights Sword is double-sword, its made from two swords - Sword of fear and sword of pain (pain and fear, because it's what slaves feel - pain from hunger and suffering and fear from not knowing what is going to happen). To make it more powerful there is Starswirl's horn inside. In my opinion she is the most powerful evil-mare what could there be, because her talent is magic and that means she is unstoppable+enslaving.
Her magic is so powerful even her horn is in flames whole time. And everypony are screwed
Twilight Sparkle MLP FIM