Here is what the sword that Twilight is trying to hold looks like. Zweihander.

Twilight sat on Celestia’s couch, looking at a photo album while Celestia sat outside on her porch. In one hand, Celestia held a long yet simple sword. In the other, she held a whetstone. Each photo in the album depicted Celestia, Luna, Eventide, or some combination of the three, often with other family members present. However, Twilight couldn't help but notice something missing.

“That’s odd. I don’t see any photos of Eventide’s father in here,” Twilight muttered to herself. “I wonder if Celestia took them out.”

Intermittently, the sound of stone scraping along metal would disrupt Twilight's thoughts, forcing her to realign them, which began to try her patience. When she finally had enough, Twilight set down the album and got up, saying, “Principal Celestia?”

“Twilight, please don’t call me ‘principal’; I'm not an educator anymore,” she heard the regal woman reply from outside. “Call me something more informal, like 'Tia'. That's what my...sister calls me.”

“Alright. How are you feeling, Tia?”

Setting down her sword, Celestia took in a deep breath, letting it out slowly as she got up and looked out towards a wooded plot near her house. “Has Luna returned yet, Twilight?” she finally said.

“No, not yet, and that doesn’t answer my question. How are you feeling?”

“I guess I'm still angry with her for keeping Eventide's location from me. While I understand her reasons for it, it still hurts knowing what she did.”

Returning to the couch, Twilight picked up the photo album, flipping over to one of the many pages inside of it. One of the photos showed a young girl with red and yellow hair. She had a black right eye and stitches on her left cheek, while a row of stitches ran from over her right eyebrow down to her right cheek. The caption read, "Eventide, age seven. Canterlot Hospital."

“Why would you take a picture of your daughter when she was at a hospital?” Twilight said while staring at the photo.

“Huh? Oh, that. I wasn’t the one who took that. It was my father. He took that shortly after he picked her up from the hospital and started teaching her martial arts.”

“I see." A worrying thought crossed Twilight's mind. "A-Are you worried that if you find Eventide, you'll have to fight with her?”

Celestia didn’t reply right away, instead walking into another room with Twilight in tow. Getting into the other room, Twilight let out a soft whistle.

Various armors, helmets, clothing, and weapons were displayed in the room, covering almost every inch of the room's walls or surfaces. Celestia walked over to a helmet and picked it up, staring wistfully at it before sighing and setting it back down, moving to a sword and a set of daggers. Her musings were interrupted when Twilight said, staring at a suit of armor, “Is this the armor that you showed me at CHS?”

“No. That equipment actually belongs to my daughter.”

“Including this?” Twilight stared at a sword that stood six feet in length and had curved points extending from the blade about halfway up its length. “I don’t see how she could have used such a massive weapon.”

“It’s called a zweihander, and it's used in both hands.” Looking at Twilight, who had to crane her neck just to look at the pommel, with a touch of amusement, Celestia continued, “Would you like to hold it, Twilight?”

“Sure. That is, if you don’t think Eventide would mind.”

With a smile, Celestia said as she took down the massive sword. “I won’t tell her if you won’t.”

The sword's tip hit the ground with a soft thud as Twilight struggled to lift it, grunting with each effort to lift the weapon and keep it steady in her grip. Celestia couldn’t help but laugh lightly as she watched the seventeen-year-old girl struggle again and again to lift the heavy sword.

“Twist your hips. It'll help you pick it up.”

“Like this?” Twilight twisted to the right lifting the giant sword slightly off the ground. “This thing is heavy. How was Eventide able to pick it up, let alone use it?”

Grinning, Celestia was about to reply when she and Twilight both heard the doorbell ring. Looking in the direction of the hallway, Celestia grumbled, “Now who in the world would be at my door at this time of night?” Taking the sword from Twilight and putting it back in its place, Celestia left for the door, Twilight once more following along.

It wasn't long before the two reached the front door. Celestia opened it, preparing to give out to the visitor, when her words died in her throat, her eyes wide in shock as she beheld her old mentor and family friend standing next to her sister on the porch.

“S-Star Swirl?”

“Hello, Celestia. It is good to see you again.” Stepping aside, Star Swirl allowed Luna to pass him by without a word to her sister, continuing toward the same room that Princess Twilight and Celestia had just left. “Do not take offense to Luna’s behavior, Celestia. She is hurting as much as you are now.”

Seeing Twilight looking at him curiously, Star Swirl said with a wink, "And it's good to meet you, Princess Twilight."

Twilight jumped in surprise, saying, “Y-You know about me? But how?”

With a laugh, Star Swirl replied, “Yes, and I know about Equestria, as well. Luna filled me in on some of it, but honestly, the information is second-hand; she got her information from Sunset before she...well, before she passed away.” Star Swirl's tone was somber as he finished. Stepping further into the house and gently taking Twilight's hand into his own, he continued, “Allow me to fully introduce myself. I am Star Swirl Cat'an, and I am fully pleased to make your acquaintance.”

Twilight shook his hand with a light blush on her face, but something gave her pause. As she looked, she thought she saw a bit of magic gleam in the old man's eyes but quickly dismissed the thought. “It can’t be him," she thought. "Non-Equestrian magic doesn't exist here, and besides, he wouldn’t do that to Princess Celestia.”

Ending the greeting, Star Swirl softly said, “Now, I must speak with Celestia alone, if you don’t mind.”

Nodding, Twilight headed into the living room. When she was gone, Celestia said quietly, “Let’s go speak outside.”

Getting outside, Star Swirl leaned against the railing of Celestia’s porch. Taking out a briar pipe, he packed it with tobacco and lit it. Celestia watched him, letting him make the first move. Taking in a deep breath and letting the bluish smoke curl up towards his head, he said softly, “Luna tells me you want to go through the portal at the school. Is this true?”

“How do you know about the portal, Star Swirl?” Celestia asked tiredly, knowing where the conversation was heading.

“I just told you. Your sister told me about that, just as she told me about Twilight, as well as about Sunset's attempt to take over the school and about how she was betrayed by her former friends. She even told me about Equestria...and about Eventide.”

Leaning up against the railing with her arms folded on top of it, Celestia snarled out bitterly, “Oh, so she hides it from me for two fucking months but just tells you without a thought. Shows where her priorities lie!”

“That is quite enough, Celestia! Your sister means well, and as I said, she is hurting as much as you are. Do you think she wants to lose you, too? She wants you to stay in this world, where it is safer. Luna is also blaming herself for the loss--” Wordlessly, Celestia headed inside, her head bowed low. Star Swirl shook his head, mumbling to himself, “I see. I’ll have to resort to Plan B.”

Entering the house, Star Swirl followed Celestia to her kitchen, watching as she set a kettle of water on the stove. When Celestia saw him, she said sternly, “I know my sister meant well, but this--”

“Celestia, I know both you and Luna are very protective of Eventide. And who can blame you? First, you lose one daughter, then the second a decade later, and only just now do you know where she is--”

“How dare you bring that up, Star Swirl! You know damn well what that did to me," Celestia snarled as Star Swirl calmly listened. "To have your child taken from you, knowing that you should have been able to stop it, to live each day and count each birthday not knowing if she's alive or dead, is the worst pain I've ever felt. You have no right to bring her up!”

Taking another long puff and slowly letting it back out, Star Swirl said softly, “I was there, Celestia. I saw her get taken, and I saw Luna get hospitalized trying to stop it. You both did all you could, and now, when your second is so close to your grasp, I know you're ready to do all you can again. But to throw your life away in a foreign world you know next to nothing about? What good will that do for Eventide?”

Taking the kettle off the stove and setting it on the counter, Celestia stared coldly at it, saying bitterly and fighting back her rage, “I don't care. I wasn’t able to protect either my sister or my daughter that day, but now, I'm going to make sure Eventide's safe, even if it does kill me. I have no choice.”

“That is where you are wrong. You do have a choice. Let me or Twilight be the one to go and get her.”

"No," Celestia said curtly. "I'm her mother. I'll be the one to get her." With that, Celestia walked away. Star Swirl took another puff on his pipe before taking out an ashtray from within his coat pocket and tapping the ash from his pipe into it. "Okay, time for Plan C," he thought. Getting up, he said, “You know, it's a real shame there isn’t a kendo ring nearby. We could settle this little dispute and get some exercise in, to boot.”

Celestia stopped in her tracks, her eyes narrowed suspiciously. Turning around, she stared at Star Swirl, “Really? We're going to decide who goes and saves my daughter with kendo?" Star Swirl just smiled mischievously at her, and Celestia sighed. "There's one in my basement. I’ll be ready in fifteen minutes.”

“Good. I’ll be downstairs, waiting for you.”

"I'll be the ref!" Luna shouted, rushing back into the kitchen.

Twilight popped her head into the kitchen, too. "What's going on?" She looked at Luna. "Ref for what?"

Luna looked excited. "Celestia and Star Swirl are going to have a kendo match. Star Swirl's gonna kick her butt! It'll be great.”

"What's kendo?" Twilight asked curiously.

"It's a sport where two combatants attempt to score points by striking their opponent's head, wrists, neck, or sides with a wooden sword called a Shinai," Luna explained.

"That sounds dangerous," Twilight said worriedly.

"Don't worry, Twilight. Both combatants wear armor, and Celestia and Star Swirl have been practicing kendo for years. They'll be fine. Now come on, I need your help." Luna led Twilight down into the basement, and Twilight saw a large, raised mat in the center of several others, each gray and blue in color.

“Is that where they'll be fighting?”

“Yes. As for us, well," Luna pulled out four flags from a nearby stand, two red and two white, and passed a red one and a white one to Twilight before continuing, "here.”

Looking at the flags, Twilight said, “What am I supposed to do with these?”

"You're going to be a referee," Luna said simply.

"What?" Twilight asked, surprised. "But I don't know the first thing about kendo."

“Relax, Twilight, it's easy. When you see Celestia land a hit on Star Swirl, raise the red flag. When you see Star Swirl land a hit on Celestia, raise the white flag. The match will continue until one of them scores two points.”

“I see. Look, as much as I'd relish the chance to observe and learn about a sport I've never heard of, can't we all just sit down and talk this out? Emotions are running high, after all, and I wouldn't want any accidents.”

“Twilight, my sister is very angry, and if she were to go out into the city with how upset she is, she could hurt either herself or someone else. At least this way, she’ll be too tired to put up much of a fight.”

Twilight sighed, saying softly, “Alright, but for the record, I don’t think this is a good idea.”

“I know you don’t, but if Star Swirl thinks this is a good idea, I trust him."

Twilight said nothing, instead opting to get into position on the side of the ring a small distance from Luna as Celestia and Star Swirl entered the ring, both wearing unusual breastplates, thick gloves, and helmets with facemasks. They wore a simple black robe under the armor.

“Please, can’t you two just call this off?” Twilight begged. “I don’t want to watch either of you get hurt.”

"No, Twilight. I've known Star Swirl for years, so I know that if he suggested a match, there was a reason for it.” Looking to her opponent, Celestia continued, bowing, “Are you ready to begin, sensei?”

“Sensei?” Twilight blurted out.

“Twilight, hush,” Luna said.

“I am most certainly ready, my student,” Star Swirl said confidently.

With that, both combatants took their respective places. Luna held up her hand between the two combatants and waited for them to get ready. Placing her hand over the hilt of her Shinai, Celestia said, “You can walk away if you'd like, sensei. There will be no dishonor in it.”

“Wouldn’t dream of it. Now, let us begin.”

Eyeing each of them, Luna let out a soft sigh. Slightly bending her left knee and lifting her right foot so only her toes touched the mat, she screamed out, “Hajime!”

As soon as Luna leapt back, the clacking and cracking sounds of Celestia's and Star Swirl's sword's echoed throughout the basement. Twilight watched, mesmerized and enthralled, as the two battled, moving in and out, countering and parrying, and trying their best to strike their opponent. Celestia swung at Star Swirl's side, and Star Swirl parried, pushing Celestia's Shinai away and trying to strike Celestia's right shoulder. Celestia blocked the attack just in time, countering with an attack to Star Swirl's right wrist, striking the inner glove.

Seeing the hit connect, Twilight quickly raised her red flag. Luna did the same, shouting, "Kote-bu!" Hearing Luna award Celestia her point, the two combatants moved back to the center of the mat.

“Celestia, this needs to stop!" Twilight said. "Please! I don't want you to get hurt!"

"Twilight, for the last time, this is happening!" Celestia snapped. Twilight whimpered softly, and the two combatants readied themselves again.

Luna eyed the two and, adopting her previous stance, shouted, "Hajime!"

The two rushed back in, striking and countering and thrusting and dodging. Star Swirl blocked Celestia's overhead strike and attacked her side. Celestia ducked low to dodge the attack, swinging upward toward Star Swirl's exposed wrist. Star Swirl flicked his wrist, letting Celestia's attack hit the hilt guard of his Shinai and countering with a thrust of his own. Celestia dodged backward and risked a glance to the floor behind her, finding herself at the edge of the mat. Quickly taking advantage of her distraction, Star Swirl performed an overhead strike. Celestia just barely raised her sword in time to block the blow, falling to one knee under the impact. Pressing down with all his might, Star Swirl held Celestia in place.

Finally, her muscles straining under the pressure, Celestia yelled out, “Mattai!”

Backing away slightly while keeping his stance and sword ready for another attack, Star Swirl said, “Do you need to take a moment to rest, Celesta?” Celestia could hear the smirk in his voice. “You could just forfeit if it's too much for you. We won't think any less of you.”

Breathing heavily, Celestia stood up, raising her sword to an attack position and spitting, “Shut up and fight!”

Shrugging as he adjusted his stance, Star Swirl replied, “If you insist.”

“Hajime!” Luna yelled. The two lunged in, and with a speed that belied his age, Star Swirl took advantage of Celestia's fatigue, deftly moving under Celestia's attack and striking her in the side.

“Do-bu!” Luna called as the two referees raised their white flags.

Returning to her position on the mat, Celestia said, “I won’t let you win this battle, Star Swirl. Give it up, already!”

“No way. I’m having too much fun!” Star Swirl replied jovially, taking his own position again.

Luna assumed her position and yelled, “Hajime!” As soon as the word left her lips, Luna found herself ducking and scrambling to get out of way of the two combatants as they went at each other with furor, Celestia's temper at the tipping point. Star Swirl lunged in, performing another overhead strike. Celestia parried, moving fluidly and shifting her weight so that Star Swirl's momentum carried him past her and toward the edge of the ring. Lunging forward, Celestia put as much force in her swing as she could, aiming for Star Swirl's side. Star Swirl twisted and blocked just in time, but the force of Celestia's blow knocked Star Swirl off the raised mat and onto the padded mat below. Luna quickly yelled out, “Mattai!”

Celestia froze in her tracks with her sword above her head, ready to bring it down onto Star Swirl's chest. Looking to her sister, Celestia gave a nod and returned to her position on the mat while Luna quickly went to Star Swirl's aid.

“I’m alright. I don’t need any help,” Star Swirl said, brushing off Luna's hands as he got back to his feet. Seeing the worried look on Luna's face, he continued, “Don't worry, Luna. Trust me, this is more fun than the time when we all went fishing after we found out that Celestia was pregnant.”

“Didn’t you get caught by my fish hook?” Luna replied, deadpan.

“Yep!" Star Swirl replied happily. "Caught me right in the ear. I still have a scar from that. But now's not the time for reminiscing. I need to get back to the mat.” Gently placing his hands over Luna's, Star Swirl added softly, “I know how to end this, but I know she won’t like it.”

“Then do it, and do it quickly before she gets pissed enough to just run from here to the portal,” Luna demanded.

Nodding, Star Swirl got back onto the mat, readying himself for his final round with Celestia. Luna looked at her sister, then at Star Swirl. Holding her hand out between the two of them, she yelled out, “Hajime!”

The two lunged in, each trying to strike the other in the head, each dodging the blow. Celestia quickly found herself backing up as Star Swirl lunged in, performing three strikes simultaneously. Quickly blocking two of his strikes, Celestia tried to block the third when Star Swirl reached in and grabbed her wrist, catching her off-guard. As Celestia froze, Star Swirl flipped her to the ground and pressed his knee to her back. Celestia grunted in pain before yelling, “Mattai!”

“What's wrong?” Star Swirl said, letting Celestia up and taking his helmet off. “I didn’t hurt you too badly, did I?”

“What the hell was that!” Celestia spat back in rage. “You can't throw in kendo!”

Grinning while he took a knee as he tried to catch his breath, Star Swirl said, “Really? Because I just did, and there's nothing you can do about it.”

Her eyes narrowed, Celestia walked over to a nearby bench and began removing her armor. “You cheated, Star Swirl, so I win by default. I'm going to Equestria.”

“Open your eyes, Celestia!" Star Swirl snapped, suddenly very angry. "Yes, I cheated, but guess what? There are no rules in war! You have to be ready for anything, and if you force yourself to act honorably and play by the 'rules', you're just going to get killed! The three of us all love you too much to let that happen.”

"I don't care!" Celestia shouted. “She is my daughter, and I will be the one to save her! I already lost Twilight, I'm not losing Eventide, too!” Celestia fell to her knees, sobs wracking her shoulders as the other three, especially Twilight, froze at her outburst. "She doesn't even know what happened to her own sister," Celestia quietly sobbed after a time.

Star Swirl gently laid his hands on Celestia’s shoulders, pulling her into him. Hugging him tightly, she sobbed heavily into his stomach, saying through her sobs, “I was a horrible mother. The foster care, the asylum, the treatment. It was all my fault.”

“It wasn't your fault, Tia!" Luna asserted. "You're not psychic. You had no idea what would happen in that hospital. You did the best anyone could have done after everything that happened to you.”

Holding her warmly in his arms, Star Swirl very gently ran his fingers through her hair, saying softly, “You must let this go, my friend. It won’t do you any good to go to Equestria. You’ll only get yourself killed. Let someone experienced go retrieve her. We have a native of that world right here. So please let Twilight do this.”

“I can’t let it go. You may not blame me for what happened to her, but she does. I have to find Eventide and make things right with her or I’ll lose her forever. I've already lost my husband, my first-born daughter, and my job. I can’t take losing Eventide, as well.”

Seeing that her mind was made up and unshakeable, Luna closed her eyes, saying as she balled her fists tightly, “Alright. We won’t try to stop you from going anymore. Just...Just promise us that you’ll take Twilight with you. Let her watch over you and take care of you in case things get rough.”

Ending the hug, Celestia wiped her tears away, saying, “A-Alri---”

The ringing of Luna’s phone cut Celestia off. Rolling her eyes, Luna answered it.

“Hello, this is Lu--”

“Luna, it's Applejack. Ah, need you to come to the hospital right now! My granny 'n' brother have both been admitted, and Ah can’t find Apple Bloom anywhere.”