Question: Who is a fictional character in Nickelodeon's animated television series "" and "The Legend of Korra", greatly aided the previous avatar, Aang, in his efforts to save the Earth Kingdom from destruction?

Context articles: The Legend of Korra
Korra
Avatar: The Last Airbender
Zaheer
Michael Dante DiMartino
Tenzin (The Legend of Korra)
Toph Beifong
Lin Beifong
List of The Legend of Korra episodes
Avatar: The Last Airbender – The Burning Earth

The Legend of Korra is an American animated television series that aired on the Nickelodeon television network from 2012 to 2014.
 It was created by Bryan Konietzko and Michael Dante DiMartino as a sequel to "", which aired from 2005 to 2008.
 Animated in a style strongly influenced by anime, the series is set in a fictional universe in which some people can manipulate, or "bend", the elements of water, earth, fire, or air.
 Only one person, the "Avatar", can bend all four elements, and is responsible for maintaining balance in the world.
 The series follows Avatar Korra, the reincarnation of Aang from the previous series, as she faces political and spiritual unrest in a modernizing world.
Avatar Korra (寇柆 , Kòu Lā ) is the title lead character in Nickelodeon's animated television series "The Legend of Korra" (a sequel to ""), in which she is depicted as the current incarnation of the Avatar, responsible for maintaining peace and balance in the world.
 She is the immediate reincarnation of Avatar Aang (title character and main protagonist from the original series).
 The character was created by Michael Dante DiMartino and Bryan Konietzko and is voiced by Janet Varney.
Avatar: The Last Airbender (Avatar: The Legend of Aang in some regions) is an American animated television series that aired for on Nickelodeon.
 The series started in February 2005, and concluded with a two-hour episode on July 2008.
 "Avatar: The Last Airbender" is set in an Asiatic-like world in which some people are able to manipulate the classical elements by use of psychokinetic variants of Chinese martial arts, known as "bending".
 The show combines the styles of anime and American cartoons, and relies on the imagery of various East Asian, Inuit, Southeast Asian, South Asian, and New World societies.
 The series follows the adventures of protagonist twelve-year-old Aang and his friends, who must bring peace and unity to the world by ending the Fire Lord's war against the other three nations.
 The show is obtainable from various sources, including DVD, the iTunes Store, and Amazon Video.
Zaheer is a major recurring character in Nickelodeon's animated television series "The Legend of Korra" (a sequel to "").
 While he serves as the main antagonist of "Book Three: Change", his actions have lingering effects on Avatar Korra and the series' plot in the following book.
 The character was created by Michael Dante DiMartino and Bryan Konietzko and is voiced by Henry Rollins.
Michael Dante DiMartino (born July 18, 1974) is an American animation director best known as the co-creator, executive producer, and story editor of the animated TV series "" and "The Legend of Korra", both on Nickelodeon.
 He was born in Shelburne, Vermont.
 He studied at the Rhode Island School of Design with Bryan Konietzko, with whom he created "Avatar."
 Before "Avatar," Mike worked for twelve years at Film Roman, helping to direct "King of the Hill", "Family Guy", and "Mission Hill" in addition to his own animated short, "Atomic Love", which was screened at a number of high-profile film festivals.
 The dedication to his father's memory can be seen in the last episode of "Avatar: The Last Airbender".
 In a 2010 interview the president of Nickelodeon, Cyma Zarghami, confirmed that DiMartino and Konietzko were developing a new series for the network, called "The Legend of Korra".
 The series premiered on April 14, 2012, running 12 episodes for the first book "Air" and 14 for the second book "Spirits", which premiered on September 13, 2013 to 2.60 million viewers in the U.S., then the third book "Change" and the fourth and final book "Balance" of 13 episodes each.
Tenzin (丹增 , Dān Zēng ) is a major character in Nickelodeon's animated television series "The Legend of Korra", which aired from 2012 to 2014.
 The character and the series, a sequel to "", were created by Michael Dante DiMartino and Bryan Konietzko.
 He is voiced by J. K. Simmons.
 Tenzin's father, Aang, was the Avatar who preceded Korra and kept world peace by preventing the Fire Nation from destroying the Earth Kingdom during the 100-year war, which occurred about seventy years before the beginning of "The Legend of Korra".
 Tenzin’s mother, , greatly assisted Aang in his efforts to save the Earth Kingdom from destruction.
 Tenzin is the youngest of the three offspring of Aang and Katara.
Toph Beifong (北方拓芙 , Běifāng Tuòfú ) is a fictional character in Nickelodeon's animated television series "" and "The Legend of Korra", voiced by Jessie Flower in the original series and Kate Higgins and Philece Sampler in the sequel series.
Lin Beifong (北方琳 , Běifāng Lín ) is a major character, voiced by Mindy Sterling, in Nickelodeon's animated television series "The Legend of Korra", which aired from 2012 to 2014.
 The character and the series, a sequel to "", were created by Michael Dante DiMartino and Bryan Konietzko.
 Lin’s mother, Toph Beifong, greatly aided the previous avatar, Aang, in his efforts to save the Earth Kingdom from destruction.
 Lin is the older of Toph’s two offspring.
"The Legend of Korra" is an American animated television series created by Michael Dante DiMartino and Bryan Konietzko.
 A sequel to "", the series first aired on Nickelodeon in 2012.
 Like its predecessor, the series is set in a fictional world inspired by Asian and Inuit cultures, and inhabited by people who can manipulate the elements of water, earth, fire or air through an ability called "bending."
 One person, the "Avatar," has the ability to bend all four elements.
 Reincarnating in turn among the world's four nations, the Avatar is responsible for maintaining peace, harmony, and balance in the world.
 Korra, the series' protagonist, is the next incarnation of the Avatar after Aang of "Avatar: The Last Airbender".
 Four seasons with a total of 52 episodes have aired.
Avatar: The Last Airbender – The Burning Earth (known as Avatar: The Legend of Aang – The Burning Earth in Europe) is a 2007 video game for Wii, Nintendo DS, Game Boy Advance, PlayStation 2, and Xbox 360 based on the animated television series "".
 It was one of the last games released for the Game Boy Advance in North America and Europe.
 The game was followed by a sequel, "", around a year later.