Albedo is the Chief Alchemist and Captain of the Investigation Team of the Knights of Favonius. He is known as a genius in alchemy, even being called the Kreideprinz (Chalk Prince), and is the one that made Mondstadt known for its alchemic revolutions.
The alchemy that Albedo brought to Mondstadt is known as the Art of Khemia, and is a form of alchemy from Khaenri'ah. According to the character stories, not even Sumeru scholars knew of it.
According to his character stories, Albedo had no memory of any kind of blood relations, his only family he could think of was his master, Rhinedottir. However, after finding an artifact, his master left him and left just a few bits of instructions and his final assignment.
To show her the truth and meaning of this world. He appeared in Mondstadt with a reccommendation from his master, and with the help of the famed adventurer, Alice, he became part of the Knights of FavoniusLater. The knights, Alice, and her daughter, Klee would then become his new family.
For a while after Albedo's release, many players speculated that he was a homonculous (artifical human being), based on his character stories, his constellation (featuring a baby in something like a womb), and his voice lines. It wasn't until a Dragonspine event story that Albedo would confirm this himself.
It was through this same event that he reveals that he and Durin are brothers, made from the same creator. In stories from within the game, it was stated that the evil dragon, Durin, was created by the famous Alchemist, Gold, and as many players had theorized then, Rhinedottir was in fact Gold.
Gold, as stated earlier is Rhinedottir, is one of th Five Sinners of Khaenri'ah. The five sinners are people who were considered the best among all their peers and eventually fell to the call of the abyss. They split amongst themselves a power that could destroy the world, and when the cataclysm arrived, they did not lend the people of Kheanri'ah their help.
As stated earlier, she is the creator of Durin and Albedo, having created them through the art of Khemia. She also created the enemies that the traveler can face in Teyvat, known as Riftwolves, that come from the abyss.
She is speculated to be part of the cause for the cataclysm and the fall of Khaenri'ah's Eclipse Dynasty. Other than being part of the Five Sinners, she is also a member of the Hexenzirkel, a group of witches or mages that conduct Irminsul explorations and gather for formal tea parites, known under the codename of "R".
Durin is an shadow dragon that terrorized Mondstadt during the Cataclysm 500 years ago. With the help of Barbatos, one of the Four Winds, Divalin, slayed the dragon, and Durin's corpse fell over a mountain that would later be known as Dragonspine. However, Durin's blood was incredibely toxic and contained abyssal powers, as such, Divalin, in the process of
defeating Durin, was infected with that abyssal power. As a result, Divalin would rise again 500 years later and terrorize Mondstadt, becoming known as Stormterror.
According to the story behind the weapon, Festering Desire, Durin had perceived this event differently. Durin was hopefull of making friends with the people of Mondstadt, but seemed completely unaware of his destructive actions.
Durin even considered his poisonious blood to be a great blessing. Apparently, he viewed his fight with Divalin and Barbatos as a dream in which they danced and sang. Even after waking up with the killing blow from Divalin, it seems that Durin held no ill will to either of them and wished that
they were able to meet under better circumstances.
The main theory surrounding Albedo and Durin at this time is that in the next Dragonspine event, Albedo will lose control and Durin will revive. Many players have taken notice that the summer events tend to foreshadow major events that will happen next and the most recent summer event, Summertide Scales and Tales, where the travelers enter a fairytale world and meet paper-oragami animals as well as other characters, Wanderer, Navia, Nilou, and Kiara. These characters, along with the traveler, decide to confront the supposed "evil" dragon that has been plauging the land. Through the encounter, the Wanderer ends up seeing the memories where 2 mysterious strangers speak, talking about how it's unfortunate that the real counterpart of the dragon did not meet a happy fate, although ultimately, the dragon in the fairytale world will eventually meet the same fate as the real one. The Wanderer then confronts the fairytale dragon and tells it to remember its name, Durin. The same as the Durin that is dead in Dragonspine. Essentially, this summertime event is most likely foreshadowing the revival of Durin and that the Wanderer will likely be involved as well. So in general, there's not much to imply that Albedo will lose control himself, but he and Durin are connected through having the same creator and many people speculate that Durin's revival will either be the cause or the effect of Albedo losing control.
Fun fact: There are 3 Albedos! Technically 2. One is the Albedo that the Traveler knows, the second is a failed subject in the same experiment that had created Albedo (and had been stuck inside the stomach of Durin), and the third is one that turns into a whopperflower (a flower-like enemy) which the traveler kills.
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