Here's a presentation I made of Darth Sidious/Palpatine's Inner Circle, the collaborators and accomplices in his Grand Plan who helped him gain and solidify power from even before he became senator of Naboo to his rule as emperor.
These members of Palpatine's Inner Circle were the only persons (aside from Dooku) to know the true nature of Palpatine during his days as senator of Naboo and Supreme Chancellor and helped him into carrying his schemes out and had a huge role into turning the Republic into the Galactic Empire even before it was officially proclaimed, and would continue to serve him as most of the Highest-Ranked in the Empire.
These individuals followed him out of personal loyalty, or grand ambitions, disdain for the Republic and its values and belief in a more authoritarian and militaristic system to keep peace and order in the Galaxy, anti-alien views and xenophobia, etc...
The first and most infamous of these followers was of course Sate Pestage, Palpatine's right-hand and closest confidant who had served him from before he became senator, having been introduced to him by Darth Plagueis himself. He was also one of the only ones who knew that both Hego Damask and Palpatine were Sith lords after witnessing and helping them destroy a group of Maladian assassins twenty years before the Blockade of Naboo, and perhaps the only person Palpatine had ever sincerely considered a friend.
Pestage had a perfect knowledge of Coruscant and all of its dirty secrets, and had a large knowledge and network within the criminal underworld, being the one to do most of Palpatine's dirty work when he chose to manipulate or use criminal organisations or assassins. Along with his loyalty to Palpatine despite his own ambition, Pestage also had a sincere and close friendship with Kinman Doriana.
Pestage's loyalty to Palpatine was such that he was made his Grand Vizier of Empire, the number 2 political ruler of the Empire, and he was one of the only ones who knew about Byss and Palpatine's backup plan to return from the dead, joining and serving him on Byss until the very end of Palpatine and his own death.
Kinman Doriana was Palpatine's aide as senator, as he was born in Naboo himself, and later as supreme chancellor, and his second closest advisor and agent. A man with a troubled past who had learned certain "useful" skills, Dorian caught Palpatine's eye and was invited to become a part of his schemes and he became a key part into helping Palpatine to schedule his legal work as a senator alongside doing his dirty work behind the scenes alongside Pestage, with whom he had an instant bond and friendship upon their first meeting.
Palpatine gave him several key missions, the most famous being of destroying the Outbound Flight, a mission he completed with Thrawn that he had met and to whom he revealed that Palpatine just like the Chiss knew about a certain extragalactic species that posed a threat to the galaxy. As such he was largely responsible for the future integration and ascension of Thrawn into the Galatic Empire. He became a member of the Imperial Ruling Council until his death under unknown circumstances. Many speculated that Palpatine tried to replace him by Vader, Thrawn or Mara Jade due to how close he and Palpatine were.
Janus Greejatus was a force-sensitive human born in Chommel Minor, with a strong hatred for non-human species instilled in him by his father who had lost most of his fortune to non-human workers. His family and the Palpatine family were well-acquainted, a fact reinforced by him and Palpatine taking part in the Legislative Youth Program, and Cosinga Palpatine (Palpatine's father) was willing to send Palpatine to live with the Greejatuses to put him out of Hego Damask (Darth Plagueis)'s influence and reach, though Palpatine killed him and the rest of their family before he could.
He became a member of Palpatine's secret cabal, and served as one of his political advisors and his successor as the senator of Chommel Minor sector after his election as Supreme Chancellor before becoming one of the Supreme Chancellor's official advisors after Padmé Amidala removed him from his post for his militaristic views, through Palpatine made sure that Greejatus' xenophobic views didn't become public to not damage his reputation. He would become a member of the Imperial Ruling Council after the Clone Wars until his death on the Second Death Star.
Armand Isard was a human intelligence agent who started working for the Republic's intelligence services, eventually becoming the director of the Senate Intelligence Bureau which was in charge of the protection and surveillance of the Senate. At some point before the Blocus of Naboo Isard became acquainted with Palpatine and soon a member of his Inner Circle, sabotaging Palpatine's rivals for chancellorship by planting incriminating evidence against them before his election.
Made the Director of the Republic Intelligence, Armand Isard proved to be crucial help for Palpatine, using his increasing powers to allow Palpatine to progressively silence all opposition to him within the Republic and turning it into a more and more authoritarian state, as well as hiding crucial evidences that could lead the Jedi to Darth Sidious and terrorising or blackmailing senators into voting decrees and laws increasing his master's powers or into shutting any opposition up. He was also the man who deviced the Shadow Troopers, clone troopers with special stealthy armors and weapons specialized in intelligence and commando operations, who also were to replaced the dwindling and far too independant Arc Troopers (who were the only clones alongside Commandos who could disobey orders).
After the birth of the Galactic Empire Armand was made the director of the Imperial Intelligence, and served Palpatine for nealy 20 years more. He was also one of the few persons alongside Wilhuf Tarkin to know that Darth Vader was in fact Anakin Skywalker. Armand Isard would eventually be outstaged and outmaneuvered by his only daughter Ysanne Isard, whom he had trained and sent on a suicide mission because he was wary of her surpassing him, who had him arrested for treason and took his place. It's rumored that Ysanne herself gave him the shot that killed him.
The next member of this Inner Circle is of course Mas Amedda. A Chagrian politician and diplomat, Amedda was named the senator of Chagria and became an acquaintance of Finis Valorum and Palpatine. He became an ally of Palpatine, who arranged for him to be named Vice-Chancellor under Finis Valorum. The two worked together to sabotage and discredit Valorum, and Mas kept his position under Palpatine after his election. He became a member of Palpatine's Inner Circle, one of the only non-humans to be included in it.
When the Separatist Crisis broke out Amedda worked to manipulate Jar-Jar Binks into proposing to the rest of the Senate to grant increased powers to the Supreme Chancellor to deal with the separatists, and worked closely with Palpatine on his schemes to control the Senate and silence all opposition to him. After the Clone Wars and rise of the Empire, Mas Amedda became too a member of the Imperial Ruling Council and developped a passion for studying Sith artifacts. He was one of those who followed Palpatine to Byss until the end, while in Disney canon he became briefly the head of the Empire after Endor until he surrendered to the New Republic.
Sly Moore, one of the only non-human members of Palpatine's Inner Circle alongside aforementionned Mas Amedda, was an Umbaran woman with Force abilities that had been kidnapped by Darth Maul and imprisonned by him in a sith tomb in the Cron Drift where she endured and survived assaults from dead Sith spirits.
After such a trial she was rescued and nursed back to health by Darth Sidious, who also taught her about politics and made her one of his aides, in return she became devoted to him. After Palpatine became Supreme Chancellor she was named his Senior Administrative Aide and helped him in his plots to undermine the Republic and Jedi while increasing his power, and was one of the suspects coming under the Jedi's scrutiny when they suspected that Darth Sidous was a member of the Senate.
After the official birth of the Galactic Empire she became a member of the Imperial Ruling Council, and her relationship with Palpatine led to many rumors, with her being seen by many as the Emperor's lover and called "the Queen of the Empire", while others believed that she was the mother of Palpatine's "son" Triclops (a mutant with force abilities). It's unknown how or when she died, though rumors said that she retirered to her home Ghost Nebula and gave birth to Triclops here.
Other members of Palpatine's Inner Circle who became members of his Imperial Ruling Council included Sim Aloo, another Force-Sensitive human born on a wealthy family on Coruscant, who had been one of Palpatine's ally when he was a senator and Supreme Chancellor and who received training in the Dark Side though he was never seen using his abilities, Kren Blista-Vanee, and Ars Dangor, another one of Palpatine's naboo aides during his time as a senator. But aside from Ars Dangor, who had been give a bit more background that the other two, and who managed to survive the destruction of the Second Death Star and to serve a time under Ysanne Isard when she became the temporary head of the Empire after Endor, we don't know much about them.
Anyway, thank you for reading. I hope that it wasn't too long or convoluted, and that I taught you something. Please tell me if I forgot someone from Palpatine's Inner Circle. I chose to not include Palpatine's apprentices, even Dooku and Vader, nor the Hands of the Emperors such as Mara-Jade for obvious reasons.
