Picture for reference (Luna^^)
                               
                  I still love you. 

     Rose looked down at the letter in confusion, unsure how to respond, if she even could bring herself to. Why would Zuko send her this letter? Yet she knew it was him, even if he didn't sign it this time. 
     Angry tears overcame her, and she balled up the letter, tossing it into the creek beside her. "If you loved me, you would've stayed." she whispered to the empty woods, the darkness her only companion.
     Over and over, she thought of that last night in Ba Sing Se, of Zuko promising a future together, then of his betrayal. "I should hate you. I should want nothing more to do with you. And, yet, somehow, I still love you...and it seems I always will."
     She cursed herself for falling for someone who could never truly love her, and she cursed the destiny that brought her to this moment, her red hair waving in the wind. Then, once she had nothing left to offer the void of silence, she headed back to camp.
     That night, she dreamed Avatar Roku visited her with a message. "Rose, it's time you learned my history with Fire Lord Sozin. Not only do you need to understand the war within yourself and that of your soulmate, but you also need to understand how the war began if you want to know how to end it. Meet me on my home island on the day of the summer solstice."
     "One question: why do you care about my relationship with Zuko?"
     Roku was quiet for a moment. "Because there is a war waging inside you both and it is of my making."
     "Your making?" Rose questioned.
     "Trust me. All will be revealed during the solstice."
     "Ok, Roku." Rose agreed. "I trust you."
     With that, she rolled over and went back to sleep.
                    * * * * *
    Zuko tossed and turned, restlessly. His thoughts were too loud, reminding him of what he had done...what he had lost. That's why he was aware of a noise outside his door.
    Quickly, he rushed out into the corridor to find a scroll by his bedroom door. At first, he thought that it was from Rose, until he read it.
  
       You need to know the story of your great grandfather's demise. It will reveal your own destiny.

    What could that possibly mean?
    For hours, he pondered the letter and what it could mean. When the sun rose over the horizon and he still didn't have his answer, Zuko got dressed and headed to the corridor with the paintings of his family. On the wall were dozens of self-portraits of the various Fire Lords and Ladies that had ruled over a multitude of years. He passed a portrait of his parents and felt tears prick his eyes at the painting of his mother. Taking a deep breath, he continued until he found the portrait of his great grandfather, Fire Lord Sozin.
     "It's never too early for a sitting with the court painter, Zuko." Azula said as she walked past. "Make sure he gets your good side."
     "Wait. I need to ask you something." Azula stopped in her tracks, allowing him to continue. "What do you remember about our great grandfather's history?"
     "Oh, Zuko, it's so strange how your mind works." Azula sighed as she turned in his direction. "Fire Lord Sozin began the war, of course. He spent his early years secretly preparing for it, but he was as patient as he was clever. He famously waited for the comet--later renamed Sozin's Comet--and used its power to launch his full-scale invasion of the world. In the end, he died a very old and successful man." She sighed, bored with the history lesson.
     "But how did he die?" Zuko asked, growing more confused.
     "Didn't you pay any attention in school, Zuko?" Azula scoffed. "He died peacefully, in his sleep. He was ancient."
     The sound of Azula's footsteps receded into silence. Zuko stood rooted to the spot, more confused than before. What was he supposed to learn from this?
                          * * * * *
     Team Avatar made it to Roku's island, only to find that the island was burnt, and a village was somehow beneath the ash. Rose sat down indian style and began to meditate.
    When she opened her eyes, Roku was waiting for her. He embraced her before pulling her after him. Rose mounted Crystal, following Roku and Fang.
     "Come, Rose. It's time to visit my past. Our shared past."
                         * * * * *
     Zuko sat on his bed, trying to decipher the letter and what it could mean. Growing frustrated, he tossed it across the room where it landed on top of a candle he kept on his bedside table. The flame then revealed a secret message.
     "The Fire Sages keep the secret history in the dragon bone catacombs."
     Zuko snuck inside and found the final testament of Fire Lord Sozin. Sitting down, his began to read.
                            * * * * * 
     "As I feel my own life dimming, I can't help but think of a time when everything was so much brighter. I remember my friend."
    Roku and Sozin were the very best of friends. They grew up together in the Fire Nation and, despite their different stations in life, they spent every waking moment together. They played together, they trained and fought together. 
     For a time, they were inseparable...
                         * * * * *
   "Wait." Rose interrupted Roku's story. "You were friends with Fire Lord Sozin?"
   "Back then, he was just Prince Sozin and he was my very best friend in the world." Roku said. "Now, come, we have a party to attend."
   "Whose party is it?"
   "Sozin and I shared many things, including a birthday."
   During the party for the two friends shared birthday, the Fire Sages interrupted it by rushing in and announcing that Roku was the next Avatar.
                       * * * * *
    "Soon the day came when my friend, Roku, had to leave the Fire Nation and face his destiny as the Avatar. He needed to travel the world so he could master the other elements."

                          * * * * *
      Rose and Roku ended up in the Aether Realm. "This was the first stop on my Avatar journey. After all, every Avatar needs their Guardian and this is where I got mine."
     Roku stood before the elderly king and his young wife. "Avatar Roku, you honor us with your presence." the old king said with a smile. "As you stay with us and learn the ways of aetherbending, may you find a suitable guardian to join you on your journey to save our world."     
     Roku bowed respectfully. As he straightened up, his eye was caught by a beautiful, young woman, long, wavy hair flowing down her back, so black it was tinted with streaks of blue that matched the dress that showed off her curves and beautiful, porcelain skin. She turned her head to meet his gaze, her eyes the color of pure silver. 
     At the feast, he sat next to her. "Hello, I'm Roku."
    She looked at him from under her incredibly long lashes. "I know. I'm Luna."
    "It was love at first sight." Roku told Rose. "Sometimes you just know who you're meant for." He sighed. "While I remained in the Aether Realm, I learned aetherbending with Luna's help. We fell in love, and she joined me as my Guardian when I left for the Southern Air Temple, where I was trained to master airbending...and also where I met an old friend of yours, Monk Gyatso."
     "That's amazing!" Rose said as she saw the flashback. "I can't believe you were friends with him like Aang and I were!"
     "Some friendships are so strong; they can even transcend lifetimes." They moved forward to the next memory. "After my years mastering aether and airbending, I traveled to the Northern Water Tribe. Waterbending was especially challenging for me. Yet, in time, I mastered it as well.
   "I then moved on to the Earth Kingdom. My earthbending master, Sud, was uncompromising, stubborn, and blunt....and a lifelong friend. It was bitter work, but the results were worth it. During that time, Luna and I grew close. We married while I trained, a small ceremony with the close friends we had gained over that time. She was a beautiful bride and well worth waiting for."
                         * * * * *
    "12 long years passed before I saw my friend again. When Roku returned, he was a fully realized Avatar, and I had changed as well."
    Roku returned to the Fire Nation with his bride by his side. Sozin had become Fire Lord when his father died. Yet, when Roku came home to see his friend, it was like no time had passed at all. They were still the best of friends.
     "After all these years, he was still my best friend and, a few months later, when Luna and I had our official wedding ceremony, Sozin was my best man."
     "By the power vested in me, I pronounce you husband and wife."
     Roku turned towards Luna, lifted her veil, and kissed her. 
     "You see, Rose, when love is real, it finds a way. Love is the purest form of magic. Of course, being the Avatar doesn't hurt your chances with the ladies either." Roku chuckled and Rose managed a laugh. "Just as Luna and I were meant for each other, so are you and your prince. Finding love is hard but when you do, you run to it and never leave."
     Rose forced a smile through her pain, feeling torn. Should she forgive Zuko? Could she bring herself to do that, knowing that she still loved him, and he felt the same?
                         * * * * *
     "On wedding days, we look to the future with optimism and joy. I had my own vision for a brighter future."
     During the celebration, Sozin interrupted. "May I borrow him for a bit?"
     Luna laughed. "Alright but bring him back soon."
     Sozin and Roku walked away from the party. "What's on your mind?"
     "I've been thinking hard about the state of the world lately."
     "Oh, Sozin. It's my wedding. Can we forget about the state of the world for one day?"
     "I know, I know." Sozin said. "But just hear me out. Right from the start, I was destined to become Fire Lord and, although we didn't know it, you were destined to be the Avatar. It's an amazing stroke of fate we know each other so well, isn't it? Together, we could do anything."
     "Yes?" Roku agreed, confused at what his friend was getting at.
     "Our nation is enjoying an unprecedented time of peace and wealth." Sozin continued. "Our people are happy, and we're so fortunate in so many ways."
      "Where are you going with this?"
      "I've been thinking we should share our prosperity with the rest of the world. In our hands is the most successful empire in history, aside from the Aether Realm. It's time we expanded it."
     Roku immediately turned down his proposition. "No! The five nations are meant to be just that, five."
     "Roku, you haven't even stopped to consider the possibilities."
      "There are no possibilities. I will hear no more about this."                                           * * * * *
   "That was my first real test as the Avatar." Roku explained. "Unfortunately, it was many years before I learned that Sozin had gone ahead with his plan, despite my warning."
    Roku eventually learned that Sozin had taken over many Earth Kingdom colonies. He confronted his old friend, causing a fight. Roku won the fight, but he may as well have lost for all the good his warnings did. He spared Sozin, breaking off his friendship afterwards. And, that, was his biggest mistake.
     "Sozin and I didn't speak or see each other for 25 years after our battle. I spent most of my spare time here at my home with my wife and the many children we had together."
      One night, those 25 years later, a volcano erupted on the island he and his family called home. Roku fought but was overcome by the noxious gas. Sozin left him there to die, remarking, "Without you, all my plans are suddenly possible. I have a vision for the future, Roku, and I can't have you in the way. I'm sorry, old friend."
     Sozin left on his dragon. Fang laid next to Roku as he died. 
     A moment later, a familiar vision revealed Rose's birth.
     "Make sense of our past, Rose." Roku said as they watched the king and queen holding on tightly to their only daughter. "Only by doing so will you bring peace and restore balance to the world. And knowing the truth will allow you to find your own happiness."
     With that, Roku disappeared, leaving Rose to figure out what her previous incarnation meant.
                        * * * * *
     "With Roku gone, and the Great Comet returning, the timing was perfect to change the world. I knew the next Avatar would be born in the Aether Realm. I sent fleets of noble men and women to destroy them, but the Aether Realm was impenetrable, so I needed a new plan. So I waited and bided my time until the Avatar was sent to the Air Nomads to learn airbending. And I wiped out every air temple.
      "But somehow, the new Avatar eluded me. I wasted the remainder of my life searching in vain. I know he's hiding out there somewhere--the Fire Nation's greatest threat. Him and his useless guardian, the last airbender."
     Zuko shook his head as he finished the letter. "No, that can't be it. Where's the rest of it?"
     He had to find the answer! He sighed as he realized there was only one person who could give him the answers he sought.
      His Uncle Iroh.
                      * * * * *
     Zuko snuck into the prison cells to find his Uncle Iroh in the same position he'd left him in the last time he visited.
     "You sent this, didn't you?" he accused. "I found the secret history which, by the way, should be renamed "The History Most People Already Know."" Zuko pulled out the letter. "The note said that I needed to know about my great-grandfather's death, but he was still alive in the end." 
      Iroh finally spoke in a low, gruff voice. "No, he wasn't."
     "What are you talking about?"
    "You have more than one great-grandfather, Prince Zuko." Iroh said, turning to face his nephew. "Sozin was your father's grandfather. Sozin had Azulon, who had me and Ozai, and Ozai had you and Azula. However, your mother's grandfather was Avatar Roku."
     Zuko set an angry gaze his uncle's way. "No. That's a lie."
    "It is nothing but the truth. Roku married Luna, his Guardian. Together, they had many children including Asami, who married your grandfather. Asami was Ursa's mother. Yes, Prince Zuko, Avatar Roku was your great-grandfather."
     "Why are you telling me this?" Zuko growled out. "A reminder that what I had with Rose was never meant to be?"
     "Oh no." Iroh shook his head. "That's just it. You are meant to be, don't you see? Avatar Roku may have shown you the way by choosing her as his successor and next incarnation. That familiar presence drew you together, but you fell in love with her of your own volition. And love is never wrong."
    Here, he paused. "But there was another reason I decided to tell you all this. Because understanding the struggle between your two great-grandfathers can help you better understand the battle within yourself. Good and evil are always at war inside of you, Zuko. It is your nature, your legacy, your destiny. But there is a bright side. What happened generations ago can be resolved now...by you.
      "Because of your legacy, you alone can cleanse the sins of our family and the Fire Nation. In you is the power to restore balance to the world."
     Zuko fell to his knees. "Then there's only one choice: I have to find her."