The moment whenPalpatinelearned thatDarth MaulsurvivedThe Phantom Menaceis significant, though it has never been shown on-screen in theStar Warsfranchise. Revealed to have survived being cut in half by Obi-Wan Kenobi in the first prequel movie, Darth Maul resurfaces during the animatedClone Warsseries. However, parts of his dark story were never revealed in the series itself.
In Dark Horse’sSith Hunterscomic,Clone Warswriter Henry Gilroy wrotethe official story detailing how exactly Maul survivedthe reactor shaft on Naboo and ended up on the trash world of Lotho Minor over a decade after hisPhantom Menacedefeat. Taking place between Maul’s official return at the end ofClone Warsseason 4 and his next appearance at the beginning of season 5, Maul and his brother Savage Opress are terrorizing the galaxy with the Jedi in pursuit.However, thisStar Warsstory is also where Palpatine first learns that his old Sith apprentice still lives.

Anakin Personally Reported Darth Maul’s Resurrection To Palpatine
Sustained For Years By His Rage and The Dark Side
Several Jedi Knights including Obi-Wan Kenobi and Plo Koon are in pursuit of Maul and his brother inSith Hunters.Meanwhile, Anakin Skywalker reports to Chancellor Palpatine that the Sith Lord they’re hunting is not Count Dooku as Palpatine presumes, but instead Darth Maul. Inquiring how the Sith Lord who tried assassinating Queen Amidala so many years ago is still alive after it was reported that he’d been cut in half, Skywalker explains that Maul must have relied on his rage and desire for revenge to sustain himself using the dark side of the Force.
Essentially, Maul refused to die and created a spider-like apparatus for his lower half after he fell into cauterizing toxic waste on Naboo, ending up on the trash world of Lotho Minor. This was confirmed in aSlashFilm interview with Gilory, revealing that his explanation for Maul’s survival was approved by George Lucas himself:

“But then there was this toxic waste, he’s kind of soaking in, and it cauterized his wounds, because it’s so burning. And then he gets put in a garbage compactor and taken to the garbage planet. And George liked it. He’s like, ‘Oh, that’s good.’ So I’m like, ‘Oh, all right.'”
However, the best part of this Dark Horse story is by far Palpatine’s reaction to Anakin’s news about Darth Maul’s survival.

The News Of Darth Maul’s Return Changed Everything For Palpatine
A Rare Moment He Hadn’t Forseen in The Force
Completely taken aback when hearing that Darth Maul lives, seeing the master manipulator and planner like Darth Sidious caught completely by surprise is a pretty rare thing in theStar Warstimeline.It was the first real moment when it was clear something had happened that Palpatine not only hadn’t foreseen, but couldn’t have even imagined. Pressing Anakin for more details, it’s clear that Palpatine was indeed blindsided.
After all, Palpatine had seemingly written Maul off as a failure even before his supposed demise. Case in point,Palpatine already been manipulating and corrupting Dookuto his cause beforeThe Phantom Menace. Once Maul was out of the picture, Sidious immediately moved to make Dooku his new apprentice.Now, Maul’s survival was a huge potential disruption to all his carefully laid plans. As such, it’s no wonder Sidious gets directly involved, capturing Maul and killing Savage himself inClone Warsseason 5 following an impressive duel on Mandalore.

Palpatine Turned Maul’s Return To His Advantage
Justifying Associations With The Sith
As entertaining as it is to see Palpatine caught by surprise, it’s worth noting that he almost immediately turns the situation to his advantage while speaking with Anakin. Pretending to feign concern over the Sith’s return, Palpatine remarks that perhaps he should begin studying the Sith. This effectively gives him another layer of protection for his secret identity and alibi.
Likewise,Palpatine “studying” the Sith also supports his future seduction of Anakin to the dark side, such as when he tells the Chosen One inRevenge of the Siththat one must examine a “larger view of the Force” or recounting the “Tragedy of Darth Plagueis the Wise”. By initially positioning himself as nothing more than a scholar of the Force, Anakin’s suspicions weren’t immediately raised when Palpatine started gradually corrupting him.
Emperor Palpatine / Darth Sidious
The senator for Naboo, Palpatine rose to power and influence during the dying days of the Republic. In reality, his public persona was just a mask; he was really Darth Sidious, greatest of the Sith Lords, and he used his political skills and Machiavellian cunning to bring down both the Republic and the Jedi. Palpatine ruled his Galactic Empire for decades, until he was betrayed by his apprentice, Darth Vader. Even this wasn’t enough to stop the Emperor, however, as he was resurrected by his followers - only to be defeated once again.
Darth Maul
Palpatine’s apprentice, Darth Maul was nothing more than a tool to winnow down the ranks of the Jedi ahead of Darth Sidious’ true plans. Discarded after he was defeated by Obi-Wan Kenobi on Naboo, Darth Maul swore revenge against all those he blamed for his past struggles - Jedi and Sith alike. Maul tended to operate within the shadows, running various syndicates, and even established himself as a true rival for Palpatine on at least one occasion. He was eventually killed by Obi-Wan in a duel on Tatooine.