I, too, was once a Jedi. Before the Order became clerical and sterilised, when there was still some passion. How things come full circle, hm, Luke?
I was a Jedi. And curiousity and ambition have ever been my most defining sins. Curiousity about forbidden things. If one is taught to avoid a thing without ever truly knowing what that thing is, desire to see it begins to eat at you.
There were no Sith in those days. They'd died with the great Lords-- Freedon Nadd, Naga Sadow.
He came to me, on Onderon, on Korriban. On Yavin IV, I was given a choice: use the Dark or die in that place. Instinct to survive was stronger than honour at that moment, surrounded and crushed as I was beneath such evil.
And so I embraced the Dark. I took it into myself so fully that any part of me that had been good and merciful died screaming.
Then I destroyed Freedon Nadd, I destroyed Sadow's creatures, and I learned all I could. Never enough knowledge, never enough pain and suffering. I could devour the whole galaxy and never be satisfied.
That is true darkness. That is the darkness that rips worlds apart, that destroyed the Republic twice, thrice, and which tore the Jedi from their very foundations. That is darkness that your Palpatine housed also within his soul, as pathetic as he may have been in the end.
And why does it continue to rise, each time you think it could be gone for good? Because there is no balance without it. The brightest flames cast the deepest shadows. Skywalkers understand that. Don't you, Lord Vader? You had to learn it through fire and agony, but you learned it. Luke. You learned it at Palpatine's hands, trying so desperately to understand. A pet, a pretty jewel wrapped up in black to set off its shine. With his slimy hands on your face, wanting to take that brightness away.
Skywalkers shine, no matter what path they take. It may be the bright glimmer of the sun on gold and sand, or it could be the dull gleam of spilled blood, but you are yourselves the embodiment of that gray light.
Guard yourselves well.