Until Their Dying Breath
AN: Star Wars, set between The Empire Strikes Back and The Return of the Jedi.
Vader's ghosts are complicated.

It is a truism of the Jedi Order that a Jedi Knight's education truly begins only when he becomes a Master: that everything important about being a Master is learned from one's student. Obi-Wan feels the truth of this every day.
Star Wars, Episode III: Revenge of the Sith, novelization by Mark Stover.

"Luke will not join you, Darth."

The crisp voice comes from literally nowhere, the meaning permeating his brain even as the suit's sensors register no new source of vibration in his environment. When Darth Vader turns from his view on space, he isn't surprised to find the blue-tinged ghost of Obi-Wan Kenobi lounging on one of the rec room's chairs. Today, his former master does him the courtesy of initiating the conversation while Vader is alone, the officers of the destroyer having found one reason or another to vacate the premises soon after he entered. He knows they think he's been more unbalanced lately, having been caught speaking to thin air several times and more prone to his killing rages than ever.

The Jedi Master is not always the immediate cause of both developments but he is the underlying reason. Luke refuses to answer his summons. Vader's mounting fury blacks out his vision; the son Kenobi hid from him refuses to accept him as father!

When his sight returns, the durasteel chair lies twisted, bent by the invisible pressure of the Force and the ghost is standing beside it, a disappointed frown on his face. Vader regrets having cut him down so quickly now. The other man hadn't accorded him that favour on Mustafar and even dead, he's a pain. "Choose someone else to haunt, old man. I tire of your incessant babbling."

"As you tired of my teachings before?" The inquiry is gentle and the ghost's smile is sad and weary. To answer would be pointless and so Vader doesn't, preferring to study the apparition instead. At the moment, Obi-Wan appears as he was before his death. Impossibly old and brought down by a multitude of years and sorrows. Once upon a time, he'd thought this man could never be undone. Beaten and defeated yes, but never truly broken. Once upon a time, he hadn't imagined they could be enemies either.

Lies and deceptions. More than a lightsabre, those were the Jedi's tools.

He isn't in the mood for remembrance, and would've snarled his next words if he could've. "Why are you here?" This is one of the expected steps in the post-mortem ritual. Kenobi will not leave before certain subjects are addressed and to be rid of him as fast as possible, Vader will comply. He'll let him criticise the Siths' philosophy and methods, gloat over their failure to crush that ridiculous Rebellion, and prophesise their end. It doesn't matter. History is written by the victors and Kenobi is merely a dead man who refuses to lay down in his grave.

"Can't I miss an old friend?"

For a second, Vader is speechless, certain his perception has failed him. This- This has never been part of their traditional encounter. Anger wells up quickly in the wake of his bafflement. Kenobi sounds wry, almost abashed, and that familiar tone makes something inside Vader burn hot and painful as he advances on the ghost. "A friend? A friend would not be trying to turn my son against me, as he turned my wife. A friend would not have betrayed me."

He cuts himself off before his voice can rise furthermore. A friend. Kenobi crippled him and left him to die slowly in the fires of Mustafar. He's had kinder enemies.

Kenobi glances up easily to meet Vader's eyes. Few people can master that trick, never knowing where to focus their gazes on the mask. Irrationally, that drives Vader madder. There was a reason the Jedi was called the Negotiator, a consummate diplomat who could smooth down the ruffled feathers of a thousand races and people with a look or a word. That he could seek to manipulate Vader so now…

"Padmé loved and believed in you to her dying breath." Kenobi is correcting mildly and Vader --stops.

"You lie."

The ghost's look is unreadable, never gazing away as he bows briefly and changes subjects. "I miss a friend of mine. He wasn't the Jedi he could have been but I thought it was for the best for he was a good man. The very best I had ever been given to know."

Vader wants to snort but there is a pressure on his lungs that prevents him from succeeding. "That man was a fool and dead beside," he manages to force out, controlling his breathing carefully.

Kenobi merely smiles. "Maybe. Do you realise, we never stop learning, Darth? Right now, I'm following a crash course in faith, hope and love."

"Love? From a Jedi?" This time, he does laugh. The idea is preposterous. "The Jedi lived by rules and principles, repressing their emotions and they never came down from their ivory tower long enough to grow close to other people, let alone love them, Master."

The other man acknowledges the hit before giving him a sad once-over. "We both know I made a very poor Jedi, from more than one point of view." Now, he acknowledges the result of his actions on Mustafar but Vader is beyond anger, suddenly tired. "I made a very poor excuse of a man and teacher, too. I taught you everything I knew except how to think by yourself."

"Do not flatter yourself. I chose to serve Palpatine with my eyes wide open. Nothing you could have done would have changed that."

A moment passes in silence and Kenobi sighs, finally looking away. "The end is near. This will be our last talk, I think."

"Good riddance." Vader offers, making Kenobi turn back and narrow his eyes.

"Well, I can tell my success in the matters of making Skywalker boys listen to me is about as moderate as ever."

Vader's focus sharpens at the words. Too late, he realises the ghost might have an agenda coming here. "What are you playing at?"

"Play?" the ghost tilts his head. "I do not play, I merely serve, but the will of the Force is inscrutable, even for me as I am. I can only do as I see best. Will you ever forgive me for failing you?"

"As you've forgiven me for killing you?" Vader mocks.

Instead of answering, Kenobi bows and starts to fade, hands clasped under his robes in the traditional Jedi posture. At the last second, he looks up, giving Vader a clear view of blue eyes as he states quietly, "I always knew you would be with me when I died."

"That's not an answer," Vader remarks, unsettled.

But Kenobi is already gone.