Dimitri is unceremoniously dragged up from the dirt and forced onto his knees by a pair of imperial knights, who hold him in preparation for their liege's judgment.
For all that the years have done to Dimitri, they have been far kinder to Edelgard. She stride forth regally, clad in the striking crimson garb of the Adrestian emperor, appearing as though she has been untouched by the ravages of war. Dimitri would think that she had been standing back and letting her underlings get their hands dirty, yet he himself had watched his once-stepsister wreak graceful carnage upon his countrymen with her own hands.
It was when he caught sight of her, embroiled in the pitched melee on the frontlines, did Dimitri abandon both his reason as well as his cadre of generals and soldiers, feverishly pursuing his bitter rival across the entire battle, so eager was his desire to see Edelgard broken before him. He longed to make her pay for the Tragedy of Duscur, her betrayal of the church and the professor, and the countless lives her pointless war had claimed. Yes, he would have taken great pleasure in her suffering and eventual death at his hands.
But it was only that: a delirious vision granted to him by his insatiable need for vengeance. In reality, he now kneels on the ground before his enemy, embarrassingly easily defeated. Tempest King and legendary relic weapon or not, no one warrior can simply stand against an entire army singlehanded, let alone the emperor's elite contingent of personal guards. Though Dimitri is defeated, he can at least appreciate that he had not made it easy for his foes, as evidenced by the numerous bodies that litter the grove around him.
"Face me, coward," Dimitri growls his demand, even though his hardly in a position to do so. His one good eye burns with baleful rage, as if the raw emotion itself could slay Edelgard. "This is between us, and us alone."
Edelgard stares down at her stepbrother, her piercing violet gaze filled with neither regret nor rage, a stark contrast to Dimitri's own. In fact, her eyes are completely empty, a disturbing void of emotion or feeling. There is only a cold, calculating intellect that masks her ambition.
"That's what makes us different, Dimitri," Edelgard says flatly. "What they say is true: you really have lost yourself to your madness, to your obsession with my death. I, on the other hand, do not fight for myself. I walk a bloody path, but I fight for an ideal. A brighter future for every person in Fodlan."
"Mad? Perhaps I am," Dimitri chuckles mirthlessly. "Yet even I am not so deluded to believe that I wage this war for some lofty greater good. Yes, your death would end the war, but that really is secondary to just seeing you die. You are nothing but a murderer, Edelgard, and you will know justice—if not at the tip of my spear, then at the blade of the goddess herself. Your atrocities will never be forgiven, Flame Emperor."
"Flame Emperor. . .yes, I once donned that title." Edelgard looks away from Dimitri, both in reminiscence and an inability to look him in the eye. "You may not believe me, but I truly did not orchestrate the Tragedy of Duscur. . .we were family, once. I truly cherished—"
Dimitri howls with maniacal laughter, interrupting Edelgard. "Yes, 'once.' You think you can wash your hands of our blood, 'El,' so easily? You may allegedly have had no hand in the Tragedy, yet you ally yourself with those who did. Your alliance with those fiends is tantamount to an acceptance of responsibility."
"Perhaps it is," Edelgard mutters. "I would that I could wipe them from the face of the land, Dimitri. You are not the only victim in their millennium-long grudge." She raises a clenched fist, willing the Crest of Flames to manifest in the air, the unearthly glow illuminating the surrounding trees. "Like the professor, I too bear the crest of the King of Liberation. Neither of us were born with it, though—the professor was a product of the church's quest to resurrect the goddess, but I am the crowning achievement of those who seek vengeance upon the church. But I refuse to be their pawn, nor will I accept the rule of the church that seeks humanity's stagnation."
Dimitri's eye widens in wonder and disbelief as he beholds Edelgard's second crest for the first time. But though Edelgard has furnished the evidence to support her claim and justify her stance, Dimitri can't just let go of his hatred for her. To do so would be to let those who died forever rest without peace, to acknowledge that justice is not so black and white as he would like to believe. And yet. . .he finds his own resolve shaken, even if he can't forgive Edelgard. Was he really just a tool of the church? To Dimitri, the idea of being used is almost as unpalatable as letting Edelgard live. Almost.
"Finish, it El," Dimitri says, but this time there is no mocking venom when he says her name. There is tired resignation and a new lucidity to his voice, the whispering edge of madness gone. All that remains is but a man humbled by defeat.
"Yield, Dimitri. Yield, and you and your country will be spared. My quarrel is with the church," Edelgard says, no, implores.
Dimitri bows his head with a grimace, refusing the offer and accepting his fate. "You and I, we cannot exist in the same world, El. . . . Can you promise me that you won't harm them? My people?"
"I promise."
Edelgard dons Aymr and raises her axe to prepare to finish it. She hesitates for a moment as she looks down at the defeated king, and in her mind she can once again see the young boy from Faerghus, the young man at Garreg Mach. But if she is to walk her path, Edelgard cannot afford to fall pretty to such sentiments, but she does allow herself one final farewell.
"Goodbye, Dimitri."
With all her might, Edelgard strikes.
But to both her shock and (surprising) relief, her arm refuses to obey, and a quick glance behind her tells her why. Extending from the trees behind her are the segments of a whip-like blade, humming energy of a crest. The blade has tangled itself around Aymr, and the sword's wielder deftly wrests the relic from Edelgard's grasp, sending the legendary axe flying off into the woods.
At the same time, a buffeting wind bludgeons Dimitri and the armored knights restraining him, sending all three tumbling flat to the ground as a massive wyvern positions itself between Edelgard and Dimitri.
"Looks like we were just in time, Teach!" Claude says nonchalantly, but Failnaught's tense bowstring belies his easygoing nature.
Byleth steps out of the thicket, the Sword of the Creator still burning crimson. She looks from Dimitri to Edelgard, both startled into bewildered silence, while Edelgard's warriors mill about, waiting for the order to engage the new enemy. Calmly, Byleth lets the energy of her crest recede from the sword and approaches the three leaders. "So it would seem."
Notes: If you're wondering, for the purposes of this story, Byleth technically doesn't choose one House to teach and support. That kind of struck me as a little weird (besides the whole nameless mercenary becoming a professor of a prestigious military academy thing), that each House had a specific primary teacher who mostly did not have extensive knowledge of every topic. It makes more sense to me that it would be like actual school, where each House/class would rotate to different instructors for different classes, while having a so-called "homeroom" instructor who would handle various housekeeping matters regarding the students. So Byleth (ostensibly) would be closer to a melee combat/tactics instructor, while Hanneman and Manuela would have their own niches, and the students would have classes with every professor. Yes, there are seminars in game, but it made more sense to me that each professor would have more of a role in every students' education.
You might note, however, that the events somewhat mirror the Blood of the Eagle and Lion, with some important distinctions. That she arrives with Claude is not an indication that the story will be going the Golden Deer route.