Darth Plagueis the Wise is a Dark Lord of the Sith and master of Darth Sidious, the Emperor Palpatine.
A Sith Lord with the ability to cheat death and create life, Plagueis is the mentor of Sheev Palpatine / Darth Sidious, who, in accordance to the Sith's Rule of Two, eventually betrays Plagueis by murdering him in his sleep, taking his place as Sith Master.
Because as soon as Kylo defeated Snoke, Darth Plagueis infected him. He is no longer Kylo Ren, he is now assumed by Darth Plagueis, and it is Darth Plague's desire to rule.
Master of Darth Sidious
The time period of when Plagueis came to possess his Sith apprentice was unknown, but the Dark Lord chose Sheev Palpatine, a human from Naboo, as his apprentice.
Palpatine more or less told him the truth. Plagueis DID discover how to live forever sorta via cellular regeneration. This was possible through dark side experiments. The only parts Palpatine lied about was that he knew what they were and would teach Anakin to save Padme.
After some investigating, Darth Plagueis found Anakin on Coruscant. Plagueis remained in the shadows, he reached out with the Force and saw a vision of Anakin's future. He saw of dark armor and a dark helmet, rising from an operating table. He knew then that this boy would forever change the course of the galaxy.
Why Darth Plagueis Was Terrified of Anakin But Sidious Embraced and Trained Him - YouTube.
1 Darth Sidious
There has been no Sith, as powerful, meticulous, nor as evil as the Emperor himself, Darth Sidious. As previously mentioned, Sidious trained in the Dark Side by Darth Plagueis before Sidious killed Plagueis in his sleep, making Sidious a Sith Master.
These factors combined seemingly indicate that Star Wars' Darth Plagueis was more powerful than Palpatine, although the latter's ability to manipulate others gave him a significant edge over his Sith Master.
Requesting that Githany secretly teach him Force techniques she learned from the masters, Bane also began private lightsaber combat instruction with Kas'im.
In Legends it's pretty much confirmed that Anakin was born of the Force as a reaction to Plagueis and Palpatine growing stronger in the dark side, however the reason for his conception is much less clear in Canon.
The Rise of Skywalker (2019)
Snoke's voice is briefly used by Palpatine when talking to Ren. It is revealed that Palpatine had created Snoke as a puppet to lure Ren towards the dark side, and to reclaim the galaxy through the First Order.
Palps recounting Darth Plagueis's story to Anakin. Plagueis had attempted to glean the secret to eternal life. According to the theorist, Palpatine learned this secret from before killing his master. However, instead of cloning himself at first, Palpatine cloned Plagueis, resulting in Snoke.
Mission to Mathas. Padawan Windu was trained in the ways of the Force by Jedi Master Cyslin Myr. Following his early trials as a youngling, Windu attained the status of Padawan by becoming Jedi Master Cyslin Myr's apprentice.
Triclops Palpatine (son) Kendalina (daughter-in-law) Ken Palpatine (grandson) Mara Jade Skywalker (surrogate granddaughter)
In the final installment, however–Star Wars: Episode IX - Rise of Skywalker–it is revealed that Snoke was seemingly nothing more than a synthetic puppet created by Emperor Palpatine.
If Qui-Gon had survived his fight against Darth Maul, he would have sensed Palpatine's evil, and Anakin wouldn't have become Darth Vader. Thus, while Qui-Gon was less powerful than Yoda, Palpatine feared him more.
Darth Plagueis
The only way he was beaten was in his sleep, as he was betrayed by the one person who he believed would protect him with his life. Because of this immense power that Darth Plagueis had, it's a safe bet that Darth Vader would not be able to overpower him in a fair fight.
Palpatine killed Plagueis because his usefulness was at an end. Similarly, Palpatine viewed his future apprentices the same way he'd come to see his master. They were all tools to be discarded when they had served their purposes in his greater plans.
Sidious is also known as The Emperor of the Galactic Empire. He rose to power in the Senate as a Senator from Naboo and lived a double life as a Sith Lord. Sidious is extremely powerful and held very complex knowledge of techniques to master the dark side's force energy.
Truly, the most powerful Sith Lord was Darth Sidious, better known in his public persona of Chancellor (later Emperor) Palpatine. Through cunning and manipulation, Sidious killed his master to claim the mantle of Dark Lord of the Sith.
killed by an Imperial strike team, his dark side, like many Seth before him, refused to let go of life.
According to Star Wars Legends content, the first Sith was a former Jedi Master, Ajunta Pall, who became a so-called Dark Jedi, or “Fallen” Jedi. As the name implies, these Force-sensitives chose to practice the Dark Side, and rejected the Light Side of the Force.
Lightsaber Skills: Plagueis was also skilled in Lightsaber combat, although he disdained using his blade in combat, regarding Lightsaber duels as tedious affairs; his master viewed his apprentice as a master of the art.
His birth came about because of the schemes of the reigning Dark Lord of the Sith, Darth Tenebrous. Tenebrous compelled a force-sensitive Muun female to seduce Caar and thus create a child strong in the force, Darth Plagueis.