this is a disclaimer.
AN: allasso is Greek for 'to change/mutate'.
allasso
Treachery is the way of the Sith, but Vader (has broken too many of his promises to ones who meant more to him than Sidious) has no interest in overthrowing the Emperor. Power for power's sake holds no fascination for him – much to the disappointment of the Emperor, of course, who grasps for more of it with every breath he takes, both in the Force and the physical world. He opens himself ever further to the Dark Side and uses it to gain control of men's minds, to centralise power in the Empire and subjugate those who try to resist.
But the more Sidious surrounds himself with the power of the Dark, the more it rules him, blotting out the human qualities that once helped him become what he is.
Vader notes every opportunity to strike him down and take his place dispassionately: the opening is there, but he knows he has not the power to make something of it. Sidious is sunk so deeply in the Dark Side by now that Vader wonders sometimes if the man is even capable of dying, or if he is so much less than human now that he cannot truly be said to be alive anymore. If Sidious has, in a way, become the Dark Side.
Healed and whole, Vader might well have done it. Trapped like this, twisted, ruined – no.
Sometimes he still manages to blame Kenobi for that. More often, he cannot find it, the all-consuming hatred, the anger he once held for the man who had the gall to call him brother while leaving him to die.
He senses their secrets, Kenobi's and Sidious', bound together like a web woven around him in the Force; it would not take much effort on his part to reach out and rip them away, fragile as gossamer, to reveal the truth beyond. But there is a weariness in thinking of Kenobi, much like the detachment in his observation of Sidious' increasing insanity, and the Lord Vader is – not content, never at peace – but perhaps comfortable, leaving matters as they are.
Change, for him, has never brought anything less than disaster. Vader has no objection to upholding the status quo for a while longer.