"I'll admit she did better than I expected."
The spirit who spoke still wore the form of the man he had once been, and looked much as he had when he had died – a tall man, old but hale, with sweeping white hair and beard. He was clad, however, in the robes of a high lord of the Fire Nation rather than the simple sleeping clothes he'd died in, and atop his head was an artifact of the royal house that only the crown prince should wear. The physical copy of that artifact had been given to the spirit long ago by the man who had once been his closest friend, and he wore it still in remembrance of the person that man had once been. "She did what she did for herself," he continued, running a hand along the back of the great dragon who crouched by his side. "But she had realized now that the path her life had taken was no longer capable of sustaining her. It was enough to save her from him- this time."
The dragon bent his great head beside the spirit and nuzzled him lightly; a question seemed to shine unmistakably from his reptilian eyes. "This time, you wonder?" the spirit who had once been an Avatar named Roku whispered. "Yes, my great-granddaughter may have ruined his plans, for now, but that is not the end of it for good. He will find another way – and indeed, he may have pieces in motion already that I cannot see."
Roku turned from Fang and looked out from the top of the mountain on which they stood, from which it seemed that all the spirit world was laid out before them. "He can't give up," the former Avatar continued. "His existence is on the line. And he may yet find a way to turn Azula to his cause before this is done. They are very alike in some ways. Of course, that is to be expected, considering exactly what he is.
"I warned Sozin. I told my old friend that he was shifting the world out of balance, but all I accomplished was that he made certain I was dead before embarking on his war. He tried to break the Avatar Cycle by destroying the Air Nomads- and that atrocity still echoes in both worlds.
"Sozin was a fool to think his actions wouldn't have consequences. Even a small disruption of the balance can turn peaceful spirits into monsters – even young Aang knows as much, from his experience with Hei Bei. What the Fire Nation started with the Air Nomads and continued for a century was far worse. I warned Sozin that what he was doing was wrong. But he wouldn't listen, and then it was too late."
Roku sighed and turned back to Fang, resting one hand along the dragon's snout. "If even the smallest disruptions of the balance can create horrors, what of a century of war? He was born from the fires of the Air Temples and nurtured by a hundred years of conflict. For all that time he was quiet, basking in the light of human evil, but no more. Peace has been restored, and the power that fuels him is slipping away. Now he is putting forth all his power to ensure that the mortal world falls back into chaos- and when it does, it will take this world with it.
"Leaving him alone ruling over nothingness," Roku finished sadly; Fang made a sound deep in his throat that was too low for even his companion of nearly two centuries to interpret, save that it seemed at once comforting and foreboding.
"My time is done," Roku said quietly. "I can roam free of Aang's mind at times, but only in the Spirit World, and I have little power left to call my own. Even you, old friend, can only interact with the living rarely, when the solstice is upon us. It was my mistakes that let Sozin become what he did, but it shall be others who at last put to rest the last remnants of the evil he set in motion. We can only hope their strength will suffice." He paused and looked to the sky, and in the clouds he seemed to see the images of his great-grandchildren, and of his successor, and of others whose images remained yet unclear. Somehow that gave the old Avatar a measure of comfort, and he found himself smiling softly.
"It will be," Roku said. "It must be."
And so the first part of the Azula Trilogy comes to and end with an epilogue that pulls back the focus and sheds a bit more light on what, exactly, has been going on. This scene was rewritten heavily from the first version, in which Roku was conversing with Agni the Sun Spirit – I removed him here, feeling that I relied too much on this non-canonical character during my early Avatar fanfic-writing (though I still consider his existence probable, if only because of how the firebenders' relationship to the sun mirrors the waterbenders' relationship to the moon, and we know the moon has a spirit). I decided it was easier to just have Roku talking to himself, using Fang as a medium to bounce his ideas off of.
We learn a bit more about our spirit big bad here as well. I knew that pitting Azula against a superhuman force of evil was something I wanted to do from the beginning of writing these fics, and I'd initially toyed with using Koh for the role. That idea I abandoned quickly – I think Koh works better as a sort of creepy, enigmatic neutral than outright evil, and his grudge is with the Avatar rather than the Fire Nation royal family anyway. I knew a western-style devil wouldn't fit in the Avatarverse cosmology (before anyone mentions Vaatu, he resembles the Zoroastrian Ahriman far more than he does the Christian Satan – pet peeve) and I also knew I didn't want something that would detract from the villainy of the Fire Nation or trivialize it in the broader context of the world. Making the spirit's nature and origins tied to Sozin was a logical choice – exactly what it's the spirit of won't be revealed quite yet, but it's probably possible to guess fairly accurately.
Next fic, we'll be picking up with Azula as she starts pursuing one of the dangling plot threads from the show – what became of Ursa? (Keep in mind that the first iteration of the trilogy was written long before "The Search" was a thing, and my Ursa ended up significantly different from the canon version). However, Azula's madness is beginning to slip free of its bonds once again, the spirit who backed Azun's army is not done with the fire princess yet, and there are enemies arrayed against her who want to make sure that Ursa is never found.
All that and more when the Azula Trilogy returns in the revised and updated version of its second installment, Path of Fire.