A dark witch

Do they strive to rule the realms? Lead a horde of minions as it's master? Perhaps, they simply enjoy the act of chaos. Whatever the reasons, not just anybody with magic can be labelled a true witch. Those with the power and potential they could very well rule the world, if they aren't already are.

The idea of magic forbidden even for the magi of Arcadia should be a thing widely feared. Yet, there's always somebody. Somebody out there either brave or stupid enough, to try mastering those kind of powers. Usually, this amounts to nothing more than a wasted amount of time on their end with nothing to show for it. Or being enslaved to some demon they thought they were being smart making a contract with. But....

Every once in a while, there's a case where someone actually does it. Mastering the forces of darkness, either through training or bargaining their very soul and yet, powerful enough to serve their own will. Perhaps, their goals just happen to align with whatever forces they contract with wanted anyway. Maybe, they even found a way to turn the tables on the terms of contracts that dark gods love. And some have just dedicated themselves to training their power that much, without needing to make any kind of deals.

So, who is that is able to claim that kind of power?