We know that "ghosts are imprints of souls of [...] deceased wizards and witches" (hp wikia). And we know "wizards who fear death are likely to become ghosts" (ibid). Finally, we know (and I like the way hp.wikia phrases this) "[Voldemort] suffered from a pathological fear of death, which he regarded as a shameful and ignominious human weakness." So if Tom was so afraid of death, why didn't he come back as a ghost? Was his soul so fractured that he couldn't come back? (Was it so fractured that he couldn't go on either, stuck in limbo like/as that piece in King's Cross?)
That line is paraphrased from a quote from J.K. Rowling:
ES: MuggleNet “Ask Jo” contest winner Asrial, who’s 22, asks, “If Voldemort saw a boggart, what would it be?”
JKR: Voldemort's fear is death, ignominious death. I mean, he regards death itself as ignominious. He thinks that it's a shameful human weakness, as you know. His worst fear is death, but how would a boggart show that? I'm not too sure. I did think about that because I knew you were going to ask me that.
ES: A corpse?
JKR: That was my conclusion, that he would see himself dead.
Mugglenet and Leaky Cauldron Interview with J.K. Rowling - 07.16.05
Voldemort was trapped forever in limbo -- neither alive, nor able to move on -- when he killed Harry, and thus the piece of his own soul that resided in Harry. There was no possibility for Voldemort's spirit to take on the essence required for a person to become a ghost.
[Harry] recoiled. He had spotted the thing that was making the noise. It had the form of a small, naked child, curled on the ground, its skin raw and rough, flayed-looking, and it lay shuddering under a seat where it had been left, unwanted, stuffed out of sight, struggling for breath.
He was afraid of it. Small and fragile and wounded though it was, he did not want to approach it. Nevertheless he drew slowly nearer, ready to jump back at any moment. Soon he stood near enough to touch it, yet he could not bring himself to do it. He felt like a coward. He ought to comfort it, but it repulsed him.
“You cannot help.” [Dumbledore]
Deathly Hallows - pages 706-707 - US Hardcover
[Harry] was distracted by the whimpering and thumping of the agonized creature behind them and glanced back at it yet again.
“Are you sure we can’t do anything?”
“There is no help possible.” [Dumbledore]
Deathly Hallows - page 709 - US Hardcover
Harry has a conversation with Sir Nicholas (Nearly Headless Nick) in Order of the Phoenix.
‘What d’you mean, “gone on”?’ said Harry quickly. ‘Gone on where? Listen – what happens when you die, anyway? Where do you go? Why doesn’t everyone come back? Why isn’t this place full of ghosts? Why –?’
‘I cannot answer,’ said Nick.
‘You’re dead, aren’t you?’ said Harry exasperatedly. ‘Who can answer better than you?’
‘I was afraid of death,’ said Nick softly. ‘I chose to remain behind. I sometimes wonder whether I oughtn’t to have ... well, that is neither here nor there ... in fact, I am neither here nor there ...’ He gave a small sad chuckle. ‘I know nothing of the secrets of death, Harry, for I chose my feeble imitation of life instead. I believe learned wizards study the matter in the Department of Mysteries –’
Order of the Phoenix - page 759 - British Hardcover
It's a good-length conversation, so some might want to review it. It's in Order of the Phoenix in the chapter The Second War Begins.
Anyhow, from what we know about Voldemort, his greatest fear is death. As Sir Nicholas says above, he is 'neither here nor there,' neither alive nor dead, but existing in a kind of a limbo -- not unlike the piece of Voldemort's soul exists in King's Cross -- and unable to ever move on. I don't think that Voldemort would purposefully choose to be a ghost, because the mere existence as a ghost reminds the individual that they are dead, and being dead terrified Voldemort. To be dead and aware of it, as ghosts are, would likely be intolerable for Voldemort. My interpretation from the books is that the only state that Voldemort would be satisfied with is to be fully alive. Even if he had wanted to return as a ghost, he could not have, as that one piece of his soul remained in limbo in King's Cross. Voldemort's soul was so fractured, I question whether it would be physically possible for him to return as a ghost, even if he had wanted to.
Yes, his soul was too fractured. At the King's cross-limbo-place, Harry could have taken a train and gone 'on'. It's pretty evident that the choice of ghost/going on occurs at this place; though the place may not necessarily be perceived as King'cross. Dumbledore mentioned that the piece was beyond help. I guess that the fragments of his soul would be too spiritually weak to make the choice. The Harry-fragment certainly wasn't.
Anyways, I think a whole soul is required for ghost-ification. Remember, a fragment of a soul cannot survive without a body. That's why a Horcrux is the 'opposite' of a soul.
I think the answer is very simple- Why would he want to come back as a ghost? He can't kill anybody or gain any power or followers as a ghost. He has no friends or loved ones to stay back for.
People don't just "become ghosts". It's clearly that person's choice, based on what Nick said. I just think there would be no purpose for him to stay as a ghost. He would have no desire to.
He couldn’t - the Dark Lord is forced to exist in his stunted form.
J.K. Rowling addresses this question in an interview. She says that the Dark Lord doesn’t become a ghost, and is forced to exist in the stunted form seen in King’s Cross.
Jon: Since voldemort was afraid of death, did he choose to be a ghost if so where does he haunt or is this not possible due to his horcruxes
J.K. Rowling: No, he is not a ghost. He is forced to exist in the stunted form we witnessed in King's Cross.
- J.K. Rowling and the Live Chat, Bloomsbury (July 30, 2007)
That she says he was forced to exist in that form indicates that all other choices, including the choice to become a ghost, were taken away from him. Therefore, he could not have chosen to be a ghost. Presumably, this is because his soul was so damaged from making Horcruxes.
I agree with the theory "Voldemort is stuck forever in the limbo", but I'll add some new material. First, when Harry waked up in that limbo-like dimension, he was naked and it was all misty... Then he discovered that he could manipulate that dimension to be more "user friendly". That dimension has clearly the function of helping the deceased ones to make a choice between "go on" and "go back" (and if you go back, usually you become a ghost, Harry and Voldemort are an exeption since they're alive)... so for every wizard in the HP world, the "Limbo dimension" takes the shape of a well-known place with a similar function. For Igor Karkaroff it could be a port, for example. If a person need some clarification to make his choice, then it could be possible to meet someone able to help. It's like the "tunnel" in a Near Death Experience, but more cool...
But Harry wasn't alone in that dimension. He was with Voldemort. Why I say that the creature is Voldie and not the piece of his soul that was clinging to Harry? Easy: the pieces of Voldemort's soul inside the Horcruxes are "destroyed" and not "killed". If not, an Horcrux user would contemporaneously be dead and alive, and given the fact that even without any horcrux left a wizard could regain his whole soul by feeling regret, this method could be used to recollect informations about the afterlife. An absolute taboo in HP world, in fact only the Master of Death was able to peek a little and remember something...
The fact that Harry and Voldemort were both in the Limbo dimension despite they were both alive, is due to the fact that the Killing Curse was in fact taken by Harry, who should have died, but it's effect was diverted toward the piece of Voldemort's soul, a soul very unstable despite the nagini-Horcrux and Voldemort's body to keep it alive. Yeah, it's a very complex magical mess... No wonder that even the Killing Curse started to fail.
Why those two were in the same dimension, while one could think that the Limbo is a very personal experience? This happened because they "Wrapped their destinies together more securely than ever two wizards were joined in history", that's why.
So, Harry and Voldemort were toghether in this Limbo dimension, but not only Voldemort wasn't able to alter the dimension in any way... After harry decided to come back, he wasn't able to remember anything of the experience. Why?
My guess is that J.K. Rowling created a very awful afterlife for uncle Voldie: it is true that he's stuck forever in the Limbo dimension and he's suffering a lot, but his inability to escape from that condition is due to the fact he's barely conscious, he's unable to understand where he is and who he is, and he's nothing more than a deformed agonizing thing without any memory of his former self, forever unable to die, since Voldemort is already dead. The only slightly hope for him is an act of the love he so much despised, I'm talking about Merope or Bellatrix going to the Limbo, pick up the poor thing, put it in a stroller and take him to a better place knowing that Voldemort will be forever like that. So dantesque...