Stormtroopers know ghosts.
It isn't given to them to know much. Formal history and personal records are denied to people who have designations, not names. Their knowledge of where they are and where they came from is presented in a sanitised form, bare outlines, bloodless and standardised. Their beginning and end is the Order, and they don't need to know anything but their designations.
They do anyway.
It begins with nicknames and ends in ghosts. Finn had no nickname until he broke a high-value Resistance prisoner out of his cell, but he knew the stories, as well as anyone else. They span the galaxy. The troopers who fell when a Knight of Ren grew angry here; the cadets who gave their lives to end a violent insurrection there. The semi-mythic tales of the first years of the trooper called PH-5587 who rose to glory and a suit of chromium-plated armour. The strongholds that have been in use so long they still ring to the footsteps of the Eldest Brothers, who numbered millions and had only one face.
Most troopers can hear the whispers; many can see movement, and a large number can see more than that. If anyone has an idea of the proportions, it must be a senior trooper who has lived through more cycles and deployments than Finn's even breathed for. No-one knows if the officers can see or hear the ghosts at all, and once a story is told it is not repeated to the same listeners. If a ghost is seen it is not acknowledged. A platoon of troopers who died because Kylo Ren did not adhere to a strategic plan marched straight through General Hux during the last morale lecture Finn saw, and no-one twitched, not even Captain Phasma.
You can hide a lot behind an all-encompassing opaque white bucket, even if you plate it in chromium.
Slip liked to repeat stories. FN-2187 could talk to the ghosts. These were both disgraces to their unit, but ones that could be overcome through silence.
("You can see me," says a tall alien in plain robes, when FN-2187 is so small he's still pre-combat. With the assistance of his most recent lessons FN-2187 classifies her as Togruta, mature adult female. "You can hear me. Oh, my dear, this is not an easy path for you to tread."
Even then FN-2187 knows better than to reply.
The Togruta touches his forehead as she leaves and says may the Force be with you. FN-2187 flinches, but only because he's surprised.
She's not a trooper, but she is nonetheless a ghost.)
Finn hasn't lost his gift - or his curse, depending on how you like to see it. Slip clings to his fingers for the first few hours after his death, before Finn leaves Jakku's airspace. He searches everywhere for Poe Dameron, but Poe is not a trooper, so maybe he doesn't have a ghost.
Poe Dameron turns out not to have a ghost because he is alive, which is the best thing Finn has ever known. General Organa is trailing an entire planet behind her, minimum, and Finn can't see faces or hear names but their weight lies on her shoulders. Captain Solo's ghosts are the ghosts of his own failures and recriminations, and that is not the sort of thing Finn can see, hear or speak to.
In the half-light of Starkiller, in the darkness of the thermal oscillator station, Finn can hear the cries of the stormtroopers who were dropped into the diggings by the earliest Knights of Ren, who wanted to know when the screaming would stop. The trick is that it never does.
Finn can still hear it as he flees into the forest with Rey, even though he's increasingly unsure who's doing the screaming. He picks up a lightsaber and fights, and there's a ghost at his shoulder.
"Keep your guard up - block steady. All you have to do is buy time," says the ghost, who is tall and young and scarred. His robes are dark but they're as long and layered as the Togruta adult female's were.
"I'm trying," snarls Finn. All the prohibitions are out the window now; he's fighting for his life, so why not speak?
"Who is that?" Kylo Ren shouts. "Who's there?"
"Your least favourite lie of the Light," the ghost informs Kylo Ren bitterly.
"Could you help," Finn gasps. He understands nothing of what's going on.
"I'm doing what I can," says the ghost, frustrated. "Block higher on your left. She just needs a bit more time -"
None of it stops Kylo Ren carving Finn's back in half.
Finn comes round for the first time when they're still on D'Qar, before he's transferred to a bacta suit. Rey is gone, and evacuation is imminent. Poe has been by to tell him these things, but since Finn was unconscious at the time he has no idea.
When Finn's eyes open the room is swimming and the ghost is lurking in a corner.
"Where am I?" he says. The monitors are bleeping urgently; a droid wheels into the room and then out again.
"Awake," says the ghost unhelpfully. "That's the important thing."
Finn squints at him. "You're a Jedi."
The ghost nods. He pushes hanks of loosely curly hair off his thin, handsome face. Finn doesn't recognise him, but he is definitely not a trooper.
"You should be with Rey."
"She has my son." The ghost crosses the room, eyes the monitor that doctors are now bent over. Someone is prodding at Finn but it feels distant. "And you have a claim on my time, too." He snorts. "I have nothing but time."
"You're a Jedi," Finn repeats. Somewhere, far above Finn's head, Major Kalonia tells a nurse he must be talking about Rey; to her, Finn's words are mumbled and confused, and she can't see a scarred man swathed in dark robes.
The ghost perches on the end of his bed like some overgrown bird. "I have news," he says, smiling wryly. "So are you."
Finn has no choice but to pass out again, after that.
"You've been chatting with my biological father," General Organa says, somewhat later, looking fragile and invincible and very seriously annoyed. "Anakin Skywalker."
Poe sneezes the last mouthful of his twice-reheated caf instead of drinking it. "The Old Republic pilot? The one who flew the Denastifan Blockade?"
"The one in the sims?" Rey hazards, absently wiping caf off a literally priceless Jedi text. "With the stupid hair?"
"I've been calling him Scarface," Finn admits, passing Poe his own cup.
General Organa laughs harder than anyone Finn has ever heard.