Deep within the lower levels of the Executor is a room. In that in room there is unusually large cell. In that cell sits a togruta no older than 20. She has orange skin with blue and white striped Lekku and montrals. There are three important rules concerning this prisoner. The first rule is that she is to have triple the normal Guard at all times with one exception. When Lord Vader himself is present. Then and only then, are all the guards to leave and stand outside the room and wait for Vader to leave. No one is to enter until he has left. Only one has ever broken this rule and lived; caption Piett. Vader had been furious, only sparing the caption due to the fact that the emperor wished to speak with him immediately. The Piett never did this again, for fear of the consequences.
The second rule was that she is never to be moved for her cell which acts as a force suppression field. The third and final rule is she never to be spoken too. The consequences for breaking these rules were clear for those that broke them never did so again.
It was only natural for those on board the Executor wonder why the women was there. Though few dared to talk about is. It had become an unspoken rule to not mention the Prisoner unless absolutely necessary. Those few who tempted fate had thought that perhaps she was once a lover. Others thought that maybe she was once his friend. It was no secret that she was in fact force sensitive. One had once dared suggest that perhaps she was a Jedi, the man had since disappeared. No one had questioned it, less they be next.
The emperor was well aware of this prisoner and Vader was aware that his master knew. Vader had not announced her presents to him. Nor had he gone out of his way to hide it. The subject was never bought up by either Sith Lord. The former Jedi padawan was of no consequence to Sidious, he knew his apprentice kept her locked away. He also knew that she severed as a painful reminder to Vader of who he once was and what he had become. She fueled his anger and hatred which only immense him further in darkness.
The women, despite the high level security had never once tried to escape. Vader had often wondered why that was. She may have only been padawan when she left the Oder but she wasn't incapable of getting past her many guards. She had been a very skilled padawan indeed. Vader had entertained many ideas as to why she had not yet tried to escape. Perhaps she knew something he himself did not, unlikely but not impossible. More likely that she did not want to face a Galaxy without Jedi, without the closest thing she had known to a family. Whatever the reason, it evaded him.
He went to see her often, despite the memories seeing the togruta fought forth. Memories of time when he had been Jedi, his former master Obi-Wan and of his beloved Padme. One now passed and the other his sworn emery. Often Ahsoka refused to talk to him, though she tried to hide the fact it was clear to Vader that she always listened. For the most part when she did speak it was to argue with him and on rare occasions she would ask him about the rebels. He never told much but she was usually able to piece the information together.
Once she had asked him what happened to him after she left the Oder. He had paused for second and she thought that he was going to lash out but he didn't, he told her. He told her about Padme his, dreams of her death, his master Darth Sidious and how Obi-wan had left him to die. She understood why he had killed the Jedi, it was in the name of his love. The only person he could be completely honest with. She understood, he had always feared losing those close to him. She understood but could not bring herself to forgive him. He killed younglings, helpless younglings and that was unforgivable.
Ahsoka herself had often wondered why she hadn't tried to escape. She was shocked when she realized, that even though she was unable to find it in herself to forgive him, she pitied him. She pitied the shadow of that man that Vader was. He had gained freedom when he became a Jedi and though it was forbidden, he also found love. He had gained everything only to lose it all. She stayed because she was the only one he could talk to. She had nothing to gain by staying, by listening and yet she did.
Vader though he would never admit it, he was grateful that she did.