Thinking aloud. Would rather see responses here than in my Holocron; thank you.

Unlike the noble Knights of Arthurian lore and Jedi legend, the Dark Knight doesn’t derive her power from God, or from the Force. When Obi-Wan Kenobi tells Luke, “A Jedi’s strength flows from the Force,” he doesn’t feel the need to say “but only the light side.” The Force, as it is, is something pure.

The Dark Side of the Force refers to something far more sinister than a mystical power that can be arbitrarily divided into good and evil. The Dark Side is a perversion of the Force.

What would such a thing look like? The alteration of the Force from its original course and state; the distortion and corruption of what was once intended.

Assuming that the Force is, indeed, an energy field that surrounds us, penetrates us, and binds the galaxy together, perhaps the most obvious clue lies in the Sith code, regarding the breaking of chains. One assumes that we must live within this mystical energy, but the Sith does not feel bound to it in the way others might. She is not bound by the same social contracts, or inherent assumptions that “all” life is sacred; she is free to establish her own social contracts and determine for herself what is and is not sacred and acceptable.

I have heard others talk about the Force as though it were a river, moving without intent, although it can appear to have intent. It is not enough for the Sith to move along with the river. The Sith will re-purpose and re-direct that river, distorting it, using it for their own ends. There is nothing passive about the Sith life. It is wholly active. The Sith is always precisely where they choose to be, at any time – including being in the process of altering that river.

As for corruption...

Well, there are only two rules in this life.

1. Don’t give away everything you know.

So where does the Dark Knight draw power from, if not the Force?

From the perversion itself; first, the desire to interrupt the passive flow; then the gradual, creeping whisper in the back of one's mind that it would be alright to do so; the justification for the horror one is actually permitting when one says, "I don't have to agree with your arbitrary values." A creeping whisper that grows into a shout, until one is left with the decision of moving the damn river or succumbing to the complacent insanity of a world where everyone follows the river without question.

Yes; the Sith reverses the flow. No longer content as passive recipients of an energy moving through her, she starts pushing her own will upon it. It emanates from within. She contaminates the Force.

Finally, she stands back to see what havoc she has brought upon the world. She lets the Force move through her again; now, it strengthens her with her own essence.