Fire, Earth, Water, and Air are the elements that one can bend in the universe of Avatar: The Last Airbender and The Legend of Korra. Yet, bloodbending, metalbending, and lightning generation can also be seen at advanced benders' disposal. In the original series, Azula shows off her bending prowess by utilizing lighting, Toph discovered how to bend metal herself, and Katara is indirectly taught how to bloodbend by Hama. But are these the only people in the universe who know how to use these dangerous techniques? How long have these other types of bending actually been around? Reddit users raise these burning questions in a recent thread by u/IronManners.
Bloodbending
Hama is recorded to be the first person who learned how to bloodbend. She discovers it after being captured by the Fire Nation during a raid in the Southern Water Tribe. After realizing she can bend the water in elephant rats running around in her cell, she waited until her bending was enhanced by the full moon and discovered she could control their bodies by bending their blood. After Team Avatar discovers she is imprisoning innocent Fire Nation people, Hama turns on them. Katara is eventually forced to use bloodbending against Hama in order to help everyone escape. Realizing how dangerous it is, Katara eventually outlaws bloodbending after the Hundred Year War.
In Legend of Korra, through a flashback, Aang is shown in attendance of crime lord Yakone's trial. He breaks free of Yakone's bloodbending by going into the Avatar State. When an Avatar enters the Avatar State, they are possessed by past lives in order to harness their ancient powers. For example, Aang can be seen firebending before actually learning how to through Roku's spirit and the Avatar State. Therefore, one can conclude that in order to overpower Yakone's bloodbending, Aang would have had to consult a past life who knew how to bloodbend. Does that mean there were already bloodbenders beside Hama? There are no known bloodbenders before her, but the previous Avatars pre-date her by quite a lot.
That said, bloodbending can be overpowered by simply being a more powerful bender than the one using it. Katara was seen resisting Hama's bloodbending because, as she says herself, she is a more powerful waterbender than Hama. In The Legend Of Korra, Amon can also be seen resisting Tarlock's bloodbending because he is more skilled than his bloodbending brother. But, since they are both the sons of the crime lord Yakone, they both can bloodbend. One Reddit user also suggests the possibility of Katara teaching Aang how to bloodbend at some point before the events of the trial. Still, in TLOK bloodbenders can use their powers outside of a full moon, unlike Hama, which disproves the theory that bloodbending is just advanced waterbending.
Metalbending
Toph Beifong is noted as the first person to discover and use metalbending. When she is incarcerated in a metal cage, she realizes she can sense the earth within the metal. This is most likely due to her natural affinity for earthbending due to being blind and having more "neutral jing", which King Bumi mentions is the key to earthbending.
Nonetheless, there is some evidence that suggests that metalbending existed before Toph's discovery. Reddit user u/respect_the_69 points out that in Season 2 Episode 16, Guru Pathik mentions the possibility of metalbending while talking about how all four elements are one and the same. This is happening at the same Toph discovers that she can metalbend, so Guru Pathik must have had some prior knowledge that it was at least theoretically possible.
Lightning Generation
Lightning Generation is a very advanced subskill of firebending and rare to be able to control. Azula and Iroh are the only people in ATLA seen using it, and it is shown that Azula learned to utilize it at a very young age. By its categorization as a subskill of firebending, one can already see that it is far more studied than the other two types of rare bending. This may be due to the Fire Nation's accelerated technological advances because of their attempts to colonize the rest of the world. There is definitely evidence that states that lightning generation has been around way before the events of ATLA though. As Reddit user u/JancariusSeiryujinn states: in the Avatar Kyoshi novels, Kyoshi's firebending teacher Rangi mentions to her that elderly people in the village have witnessed its use. This predates the events of ATLA by more than two centuries.
These three bending types seem to be uncharted territory within the events of ATLA. Besides lightning generation, viewers seemingly witness their discovery as Team Avatar saves the world. Fast-forwarding to the events of TLOK, each bending skill has been taught to many others and further developed. Although Katara banned bloodbending, it was used for evil by Yakone and his sons to wreak havoc on Republic City. Whether they were actually discovered during the Hundred Year War or not, but these powers are surely deadly if given to the wrong hands.
