One thousand years have passed since Greg's body was invaded by the demon living inside Sombra. The priest in Tartarus managed to keep it from taking complete control of him. He used the time to cultivate his appearance to match that of his position as lord of Tartarus. He didn't like the title, but the denizens refer to him as such, both out of fear and respect.
Not long after he was taken to Tartarus, the Cutie Mark Crusaders found their cutie marks. Apple Bloom got one in construction and would eventually establish a residential construction and maintanence business; Sweetie Belle got hers in singing and would become the lead singer of a pony pop band; Scootaloo got hers at an extreme sports competition and became a star on the scooter.
Twilight's friends were another matter. Applejack couldn't get over the fact that he had to stay in what would be equated to Hell and her workaholism kicked into overdrive, causing her to drop dead while tending the farm, alone and foalless; Rarity found herself a nice stallion, much to Spike's dismay, and mothered two fillies of her own; Fluttershy, despite her strong reluctance to find a mate of her own, did so, one who shared her interest in caring for animals, the two decided on a single foal; Pinkie Pie... well... she was Pinkie Pie, and couldn't settle down even if her life depended on it; Rainbow Dash found a suitable Pegasus for herself, a stallion and mothered three colts.
The years would not be kind. Everypony he knew grew up, started their own families, grew old and died. Even Princesses Celestia and Luna started getting old within two and a half centuries, and died five centuries later. In their absence, Cadance took over Celestia's role and Twilight took Luna's. Thankfully Dragons had longer lifespans and Princesses Twilight Sparkle and Cadance were far younger, so his campanions would be the two ponies and Spike.
Greg slouches on a makeshift throne, tapping his fingers on the arm. During his tenure he changed the look and feel of the place. It was a hellish looking place as one would expect from the underworld, but he changed it to be neutral territory and everyone: Ponies, Griffons, Minotaurs, et cetera, would make a pilgrimage to Tartarus to visit the spirits of their ancestors.
Princess Twilight Sparkle would make an annual pilgrimage herself with her personal guard as well as Cadance and would stay for the day. He and Twilight would play a game of Chess and chat about their years.
A Tartarian messenger approaches Greg. "Milord, Princesses Twilight Sparkle and Mi Amore Cadenza are here to see you."
Greg sits up and nods. "Thank you. Show them in."
"Yes, Milord." He says, leaving the room.
Greg stands up, walks over to his Chess table, sets up the board and three seats. After finishing, he turns back to the door and sees two very happy pony princesses. "Twilight! Cadance!" He calls. The two gallop to him and give him a hug. "It's always good to see you two."
Twilight nods. "It most certainly is." She agreed.
Greg smiles at Cadance. "And you look as radiant as ever."
Cadance blushes. "Thanks, Greg."
Discord flashes in, dressed up as a butler. "May I offer you three some lemonade?" He asks, pulling out a pitcher of chilled lemonade out of nowhere.
Twilight giggles. "Thank you, Discord."
Discord whips out three glasses, also from out of nowhere and fills them with the lemonade.
The three sit at the chess table for their annual ritual. "I believe you go first this time, Twilight." He says. The winner of the last game goes first for the next game.
Greg had the board and pieces custom made from glass with a special mineral infused to prevent the pieces from shattering should they be dropped. One side was clear glass, the other was frosted. Twilight preferred the frosted set for some reason.
Twilight opens by moving her E7 pawn to E5. "So... anything interesting happen this year?" She asks.
"Not particularly." Greg says as he moves his B1 knight to C3. "Your friends paid me a visit yesterday and they long to be with you."
"They're always with me." Twilight says, moving her B8 knight to A6. "If not physically, then in spirit."
"Of course." Greg says, moving his G2 pawn to G4. "How about you two?"
"Twiley and I have our own protogés." Cadance says as Twilight moves her F7 bishop to B4.
"That's an interesting move." Greg comments, moving his C3 knight to A4. "I remember you two talking about them last time."
"Mine reminds of myself when I was his age." Twilight comments, moving her B7 pawn to B6. Greg lets out a quiet hum. "And after a thousand years, I have finally found out how to rid you of that demon." She adds.
Greg raises an eyebrow. "Oh really?" He asks. "What would that involve?"
"The first part would need you to allow the demon to take full control of your body." Cadance says.
Greg moves his G1 knight to H3. "Let me guess, the second part would involve the Elements of Harmony."
Twilight and Cadance nod. "How did you come to that conclusion?" Twilight asks, moving her D7 pawn to D6, placing Greg's G4 pawn in peril with a bishop.
Greg moves his H1 rook to G1. "It's the only logical decision."
"We found suitable bearers in Fillydelphia." Cadance says.
Twilight smirks at Greg. "You want this game to last, don't you?" She asks, contemplating her next move.
"Any family trees we're familiar with?" Greg asks.
"One colt in particular descended from a certain... rainbow mare." Twilight says, moving her G8 knight to H6. "He also shares her element."
"The apple doesn't fall far from the tree, does it?" Greg comments, moving his G1 rook to G3.
Twilight smiles and shakes her head. "It sure doesn't." She says, moving her queen from D8 to H4.
Greg shakes his head. "You're looking for a slow game, aren't you?" He comments with a chuckle. "How soon do you two want this plan to go into effect?" He asks.
"That's the thing," Cadance says with a heavy sigh, "they're still foals at this point in time."
Greg moves his D2 pawn to D3. "Sounds like I'll be stuck here for a while."
"I know, and we're sorry about that, Greg." Cadance says, setting a hoof on his hand.
Greg pats her hoof with his other hand. "It's okay."
Twilight shakes her head. "No it's not okay!" She yells. "Had we known about it sooner, we would've taken care of the problem that much sooner."
Greg stands up and looks out to the inner part of Tartarus. "Take a look around, Twilight." He says. "If it weren't for me being here this whole time, this place would still be Hell." He turns back to Twilight and Cadance.
"Are you saying that you don't your thousand years back?" Cadance asks.
Greg shakes his head. "I'm not saying that." He says, sitting back down. "Sure I'd like to go back and see everypony alive; I'd love to go back and see Apple Bloom and her friends get their cutie marks, but what's done is done."
Twilight taps her hoof on her chin a few times, then she lights up and gasps. "I have an idea!" She exclaims.
Greg raises an eyebrow. "What would that be?" He asks.
Cadance's mouth is agape. "You're not thinking what I think you're thinking... are you?"
Twilight nods ecstatically. "I am."
Greg shrugs. "Would either of you care to explain?"
Twilight shakes her head. "I'm afraid I can't let you in on it." She says, moving a pawn from C2 to C3. "Your turn."
Greg examines the board and shakes his head. "You've left yourself wide open." He says, moving a bishop from F1 to G2.
Twilight moves a bishop from C8 to G4, taking Greg's pawn. "I want to end this quickly." She says.
Greg follows her move by moving his bishop from G2 to C6. "Check."
Twilight moves her king from E8 to F8. Greg moves his queen from D1 to D2. Twilight moves her bishop from G4 to H3, taking his knight. Greg moves his rook from G3 to G7, taking another of Twilight's pawns. Twilight moves her king from F8 to G7, taking his rook. Greg moves his queen from D2 to G5, check.
Cadance watches the fast motions of their moves with wide eyes. "This is getting intense." She comments.
Several moves pass before he learns that she wants to win again, but he's going to draw it out for as long as possible. What is she planning? He thinks back to his comment 'What's done is done'... then his eyes widen. "You're not planning on going back in time, are you?" He asks.
"I knew you'd figure it out quickly, Greg." She says with a smile, moving her knight from B4 to D5, taking his remaining knight.
Greg moves a pawn. "You know I'm no dummy."
"Yes, I do." Twilight says, moving her knight. Greg moves his pawn, taking her bishop. Twilight moves a pawn of her own. "I've got this in the bag." She says with a grin."
Greg shakes his head. "Maybe..." he says, moving his rook from A1 to A2, "maybe not."
Several moves pass, the two remain quiet, figuring out their next moves, that is until Twilight puts Greg into check with a bishop.
Greg moves a pawn from C3 to C4, blocking the bishop. Twilight moves her rook from D2 to D3, taking his pawn. "You should probably quit now." She suggests.
Greg doesn't. Instead, he moves his king to B2. I'm not done, yet."
Twilight shakes her head and moves her rook back to D2. "Check."
"Why didn't you tell me you wanted to dance?" Twilight asks, moving her rook.
Cadance groans. "Come on! Just quit already!" She says after the two continue dancing for what seemed to be an eternity.
Both Twilight and Greg laugh at her outburst. Twilight moves her rook to D1. When Greg moves his pawn to B8 and having it promoted to queen, the princesses' eyes widen. "Like I said, I'm not done yet."
Twilight moves her rook to C1, continuing their check dance. As expected, Greg moves his king to B2. Twilight moves her rook further back, from C1 to E1.
Greg moves his new queen from B8 to E5. "Check." He says.
Twilight moves her king to H7. Greg moves his rook from A8 to F8. Twilight groans. "How about we call it a draw?" She offers.
At this point, neither of them would win, so he nods. "Of course."
Cadance breathes a sigh of relief. "Thank Celestia." She says, shaking her head. "I don't know how much longer I can take you two dancing around like that."
The three stand up. "Does anypony want a tour of the place?"
Twilight looks over to Cadance and raises an eyebrow. "I think we can stay a little while longer, don't you?" She asks.
Cadance shakes her head. "As tempting as it is, I think we should make our preparations for Greg's exorcism." She says.
Twilight lowers her head. "Yeah..." She says, digging her hoof into the floor.
Greg rests his hands on both princesses, going in for a group hug. "Well, it's been a blast as always. Maybe next time we see each other, I won't need to be here." He says with a wink.
Canterlot Archives, Starswirl the Bearded Wing
Twilight and two Unicorn guards enter the wing. "Let's split up and find the time spell." She orders. The guards nod and split up. She vaguely remembers its location when she, Pinkie Pie and Spike came last. Thinking about the event made her giggle.
She trots to the location she remembered and found the spell. She lets out a relieved sigh. "I found it!" She yells to her guards.
Twilight approaches the central table, along with her guards. "Are you sure you should be doing this, Your Highness?" One asks.
She nods. "It means saving a friend from a horrible fate." She says, concentrating on the spell as well as the point in time where she wanted to go to.
"Good luck, Princess." A guard says.
In a bright flash of light, Twilight finished the spell and was gone.
The Crystal Empire, Crystal Castle Throne Room, 1000 Years Ago
Future Twilight appears in the throne room, in front of herself and the others. Everypony in the room gasps. Future Twilight gallops to her younger self. "Don't take him to Tartarus!" She yells. "The demon needs to take complete control!"
Celestia raises an eyebrow. "Why would we want that to happen?"
Twilight gallops to Celestia. "To destroy it, the demon needs to be in total control over his body and the Elements of Harmony need to be used against him!" Before the others could say anything, electrical energy starts to wrap itself around Future Twilight. "JUST DO IT!" She yells out before completely vanishing.
Celestia, Luna, Twilight and Cadance bind Greg as they allow the demon to take him over completely. Greg regains consciousness, black smoke billows from his eye sockets, his irises now a menacing red.
Sombra swallows hard, looking at its new host in horror. "I can't believe I allowed you to take me over."
"At least your body was strong." Greg cackles. "This creature is the weakest thing I've ever encountered." He continued, trying to free himself.
Discord pops in and tisks. "That's enough out of you, Thanatos."
"DISCORD!" He snarls. "You dare ally yourself with these puny mortals?"
With a snap of the finger, Discord teleports himself next to Greg and Thanatos. "I'm not the one who's going to die, Thanny." He says, and with another snap, he disappears.
The princesses look at each other and Twilight nods. "Let's take him to the Tree of Harmony." She says.
The princesses circle around Greg and power up their horns. The magical aura emanating begin to engulf them, then in what seemed to be an instant, a bright light flashes and the five are gone.
The four are teleported outside of the Tree of Harmony's chamber. Thanatos continues to struggle as Twilight Sparkle and Cadance levitate him and take him into the chamber.
"Are you sure this is going to work?" Cadance asks.
Twilight shrugs. "I don't know. I don't even know how long Thanatos resided in him before I used the time spell."
Twilight and Cadance set Greg in front of the tree. Celestia and Luna trot up beside the two. "I'm afraid I can't give a certain answer, nor can I tell you how long it takes for the tree to recharge." Celestia says before the tree started to glow.
One by one, the Elements of Harmony light up and begin feeding their magical energy into the element of magic.
Greg's eyes widen as the power in the center element grows stronger. "NO!" He yells out. A beam of magical energy emits from the tree and is focused on Greg. "NO!!!!"
A bright light envelopes the chamber for a moment before dissipating. Everypony's eyes had to readjust. After which, the princesses look over to an immobile Greg. They gasp and gallop over to him.
"Greg?" Twilight whispers with tears in her eyes, then she touches his chest with a hoof. Feeling his heart beat put a smile on her face. "He's still alive."
"Of course I am." He says with a groan. "Damn... I feel like I got hit by a semi."
Everypony giggles. Twilight and Cadance remove his bindings and set him carefully on the ground.
Celestia takes point, look back to everyone else. "Come on... let's take him to Ponyville."