Summer solstice

Summer Solstice
The summer solstice is a natural phenomenon, occurring when the sun is at the closest angular distance to the equator. In the avatar world, both the Winter Solstice and the summer solstice are the only times that the spirit world and the mortal world come close together enough to interact freely with each other for enough time. This event is experienced throughout The Avatar and the Fire Lord, when Aang meditates in order to communicate with Avatar Roku about the latter's past events experienced when alive, such as his friendship, friendly rivalry as well as the eventual conflict with his friend and eventual Fire Lord, Sozin. The last thing Roku discusses with Aang is his death while trying to fight off a volcano on Roku's Island, concluding with Aang's birth. Meanwhile, in the Fire Nation Capital, Zuko receives a message telling him to go to the Dragonbone Catacombs. Once there, he reads "The Last Testament of Fire Lord Sozin". It begins (in Sozin's narration) that there was a time to when he wished that nothing bad ever happened between him and his best friend at the time, Roku, indicating that Sozin still regarded Roku as a friend, while Roku did not. It talks about Roku's departure from the Fire Nation in order to learn the 4 elements shortly after learning that he was the new avatar. Many years passed and Roku came back, marrying Ta Min afterwards, with Sozin as his best man. Later on, Sozin talks with Roku about his plans to expand the fire nation, but Roku put an end to that argument. Years later, Roku realized that Sozin went along with his original plan and the two fought in Sozin's throne room, with Roku evoking the powers of the avatar state and destroying a large portion of the palace. Roku spares Sozin but says this: "I'm letting you go, Sozin, in the name of our past friendship. But I warn you: even a single step out of line will result in your permanent...end". No less than 25 years pass when the volcano on Roku's Island erupts and Sozin comes to his aid. Sozin plugs a second volcano by redirecting heat away from the lava in a similar fashion to Lightning redirection. But that volcano re-erupts and Roku inhales the toxic fumes. Roku beckons Sozin to save him, but Sozin leaves, saying his final words to his former friend: "Without you, all of my plans are suddenly possible". Roku is then engulfed in a pyroclastic flow with Fang alongside him. Sozin's narration concludes with him saying that he spent the last years of his life searching for Aang, who at that time was in the iceberg, in suspended animation.

Zuko then confronts Iroh, accusing him of sending the message. He (Zuko) then said that the message told him he needed to know about his great-grandfather's demise, but it was never mentioned. Iroh then tells his nephew that he was misinformed. Iroh then stated the shocking truth: "You have more than one great-grandfather, Prince Zuko. Sozin, is your father's grandfather. Your mother's grandfather, is Avatar Roku". Iroh then proceeds to give Zuko the royal headpiece worn by the crown prince, given to Roku by Sozin before he left to master the four elements, and was presumed lost in the eruption.

Trivia

 * Because the summer solstice takes place around June 21, it can be safely assumed that that is when this episode takes place as well.


 * It has been theorized that a summer solstice can foreshadow or determine when and possibly where a total (or partial) solar eclipse would take place. This is more or less true in the avatar world, and it could be a possibility in the real world.

Effects on Firebenders
Theoretically, firebending is stronger on the summer solstice than on any other day because it is the longest day of the year. Similarly, firebending wiould be at its most powerful when the sun is at its highest point, at noon, similar to another theory that waterbending is strongest at midnight. It is known that Sozin's Comet will greatly enhance firebending powers to the point of near infinity, much like how a full moon does the same for waterbending powers. Lastly, temperature and climate play important roles in regulating the strength of firebending. In real life, fire requires a hot and dry climate in order to sustain itself for long periods of time, and the same could be said for fire in the avatar world, much like how water requires a cold (or freezing) and moist climate in order to sustain itself for long periods. If all these factors happened to coincide at the same time, firebenders could be nearly invincible.