Role in the film
Matai Shang is the Hekkador of the Thern's, his goals are mysterious and enigmatic. He and the Thern's are a race that travel the universe, organizing and feeding off the destruction of planets, manipulating civilizations in order to do so. It is his and the Therns' purpose to do so, however, as Shang mentions at one point that he and the Thern's have been doing it for billions of years.
In the beginning of the film, the Thern's arrive on Barsoom (Mars), and witness two cities, Helium and Zodanga, at war with each other, and decide to equip Zodanga with a mysterious weapon called the 9th Ray. Matai Shang and the Thern's ally themselves with Sab Than, the Jeddak of Zodanga, who plans to marry the Princess of Helium, Dejah Thoris, and kill her during the wedding ceremony. When that happens, Sab Than will rule Barsoom forever, causing it to end life there, and nature will follow its intended course, which is what Matai Shang and the Thern's want.
Matai Shang and the Thern's help Sab Than ensure his plan goes smoothly using various means including sending a Thern to destroy Dejah's invention just as she was about to show Helium the 9th Ray. Later, Sab Than and Shang come up with an idea to make Dejah Sab Than's wife and allow them to complete their plan of Sab Than becoming ruler. In order to do this, Shang manipulates the Great Martian Clan of Warhoon to pursue John Carter an earthling who mysteriously arrived on Mars, Dejah and their Thark companion, Sola, and the Martian beast Woola. Allowing Sab Than to rescue Dejah and make her reluctantly agree to marry Sab Than to end the war.
As the wedding is planned, Matai Shang meets John Carter and they go on a walk throughout Zodanga. During their walk, Shang explains to Carter the purpose of Thern's and how they travel the universe and manipulate civilizations of different planets. He also mentions that the 9th Ray weapon must remain in the hands of Sab Than, while Dejah, and anyone else with knowledge of the 9th Ray, will die. He then reveals to Carter Sab Than's plan to rule Barsoom, and that when Sab Than kills Dejah, her death will seal Sab Than's reign forever, completing the course the Therns have set for Barsoom. Woola, Carter's companion, suddenly appears and attacks Shang, allowing Carter to make his escape on a flying ship. Shang, unbothered by this, returns to Helium to watch Sab Than's wedding.
However, his and Sab Than's plans are forever foiled by John Carter, resulting in the death of Sab Than and the end of the war. During the battle, Shang confronts Carter and tells him that Dejah will live, but on the condition that she will fail to prove her theory of the 9th Ray. He then drops his medallion and attempts to gain it back from Carter, Dejah and Tars Tarkas. While he is successful at retrieving his medallion, he is forced to leave the battle as Helium wins the war. Not too long after Carter's victory, Shang, using the medallion, sends Carter back to Earth before leaving Mars forever and returning to his realm. Years later, Carter would later be able to return to Mars by tricking a Thern into revealing himself in order to get that Thern's medallion.
- Matai Shang states that he as a Thern can live forever, but John Carter counters that Thern's can be killed. Meaning that the Thern's may not have always been immortal, and that it's likely do to their advanced technology that Matai Shang and the other Thern's live as long as they do.
- It is unclear whether or not he is the Thern that Carter shot in the back at the end of the film to take the medallion, as said Thern was in disguise as the time.