The Tendoushuu are a group of Amanto that not only control large parts of Gintama 's universe but are the true rulers of Earth with their main base of operations in Edo, Japan. The series establishes early on that they are the main villains in the story who influenced many of the actions and lives of most protagonists and antagonists.
With the discovery of a potent energy source named Altana, originating from planets, technology advanced by leaps and bounds. Many planets went to war over it which resulted in a group of wealthy Amanto forming an organization that in theory was meant to monitor its usage. But since they owned much of the planets that held Altana, it meant in practice that they conquered worlds with the potential energy, with Earth being the most recent conquest. It could be inferred that they were behind the decision to force Japan to open its borders to the Amanto. It was revealed that they also helped the Bakufu defeat the Joui rebels during the Joui Wars.
Ten years before, during the late Joui Wars, they encountered an immortal who willingly gave them his immortality (turning them semi-immortal) and in return, he became the new member of the Tendoushuu. In the years since, they have established themselves as the true rulers of Earth, especially Japan. The biggest symbol of that control is the Edo Terminal, which sits on a gate over the biggest of Earth's Altana holes, an area where Altana leaks out of.
It is established that they run many shady businesses, like Rengokukan. They also control many human and Amanto government officials which also include the 13th Shogun, Tokugawa Sada Sada. It is also implied that they have indirect control over the Harusame and probably other space pirates.
For the past twenty years or so, they gained control of the Tenshouin Naraku, that was further cemented when its former leader, Utsuro, became a Tendoushuu member and his strongest loyal disciple, Oboro became the new leader.
Although it is known that they consist of twelve members, it is unknown if they have a hierarchy. They are commonly depicted as sitting on twelve pillars in a circle on a spaceship where they're shown mocking their enemies and praising their superiority.
They controlled an underground arena called Rengokukan. When Sakata Gintoki came to fight against Ojinishi in the arena, one of the Tendoushuu watched the fight and realized that Gintoki had the eyes of a real samurai. Shortly after, the Shinsengumi and Yorozuya put an end to the arena as the Tendoshu withdrew.
The priestess sisters, Mone and Ane, reveal to the Yorozuya about how the Tendoushuu took control of their former home to turn it into the Edo Terminal. Their shrine-home was a opening to the life energy source called Ryuumyaku (Dragon Veins). In the later Rakuyou Arc, Ryuumyaku is revealed to be another name for the Altana.
The Tendoushuu were observing Sahadaru's berserk state, though noted it as no grand threat to them.
The Tendoushuu are shown to have control over Sada Sada and the Naraku. They arrive to save Sada Sada from the revolt to his power. But his nephew, Tokugawa Shige Shige decides to stop them by resigning as shogun so his uncle will be able to be punished by law. Shige Shige is later temporarily restored to power.
In their ship, they discuss how their puppet Sada Sada had been brought down by his own ego and pride. The Naraku leader, Oboro, tells his masters that the Tendoushuu's true enemies were the students of Yoshida Shouyou. This is shown by how Gintoki's influence had lead to the "revolt" in the first place and how Takasugi Shinsuke killed Sada Sada and is implied to be in league with the Hitotsubashi Faction, later confirmed in the Shinigami Arc.
The Tendoushuu arrive in the Iga ninja village to confront Shige Shige. They reveal that they had a hand in getting Hitotsubashi Nobu Nobu to betray his alliance with the Kiheitai to become the new Shogun and their puppet. They also had a hand in getting the Harusame to betray one of their own divisions, the 7th Division, lead by Kamui. This greatly cripples the Kiheitai- 7th Division alliance, who end up on the run.
They were forced to withdraw when Shige Shige's faction was saved by the arrival of Matsudaira, Shinsengumi and the other police forces. But they ultimately succeed in killing Shige Shige.
A Tendoushuu member named Utsuro, arrives at Kokujo Prison Island after the Tendoushuu learned that someone had betrayed them and the Bakufu and sparked a rebellion. The member also came to fight another insurgent (Gintoki) who have arrived on the island earlier. Ultimately, the rebels were forced to flee the island after getting what they want, their leaders (Matsudaira, Kondou, and Katsura) but lose Isaburo in the process, even though their fight was separate from Isaburo's.
Imai Nobume reveals the history of the Tendoushuu along with a little of the past of its member, Utsuro.
Utsuro continues to chase after the insurgents, Katsura, Gintoki and their groups, who are now joined by Sakamoto Tatsuma and his Kaientai. By using his newly acquired Harusame, he also goes after Takasugi, his Kiheitai and Kamui and his 7th division to the Kiheitai's hideout, the planet Rakuyou. He becomes interested in fighting Umibouzu. He retreats with his remaining pirate/ Naraku forces after getting what he wants (his fight with Umibouzu) to Earth where he is summoned to meet his fellow Tendoushuu. Utsuro's disciple, Oboro tells his fellow disciples more about Utsuro's past and how the Tendoushuu maintain their monopoly on Altana. Only they have the keys, unique permanent tattoos on their palms, to open and close the Altana Gates and it is impossible to take or receive them without their willing consent.
It is revealed that the entire arc was a distraction by Utsuro so that the Tendoushuu would fail to see his true goal, using the keys forbidden to him to self-destruct a few planets' Altana Gates. This will enable the other planets to distrust and further hate the Tendoushuu, leading them to attack their base, Earth, sparking a war. The keys were given to him by some of the Tendoushuu themselves as a bargain to reverse their decaying bodies due to their bodies failing to cope with his immortal blood. The decay had lead to them staying alive despite their bodies falling apart, including losing the limbs that contained the keys.
Over a month passes after Utsuro's meeting with the Tendoushuu at the end of the Rakuyou Arc. The Amanto whose planets were destroyed by the destruction of the Altana Gates formed an army called the Altana Liberation Army and had liberated planets from the Tendoushuu's control until reaching Earth to both liberate (control) it and find the group, who have vanished during this time. As Nobu Nobu negotiated with the army to bring the Tendoushuu to them, it is revealed that some of the Army already knew the Tendoushuu's whereabouts. It is implied that almost immediately after the Tendoushuu meeting, Utsuro blew up the ship and it crashed on Earth. Utsuro and the Tendoushuu survived but unlike Utsuro, the Amanto group's bodies were mostly destroyed, leaving mostly pieces behind. The Army found them and had kept them in pods ever since.
Despite their mission being accomplished, one of the Army's leaders decides to continue the war with Earth to satisfy their revenge and chooses not to tell the rest of the army and Nobu Nobu about them.