In Legends, the night before Darth Sidious was elected Chancellor of the Republic, he and his master, Darth Plegis, retired to Plegis' penthouse on Coruscant to celebrate Palpatine's eminent victory. There, Sidious plied Plegis with wine while rehearsing his chanceery acceptance speech slated to be delivered the following day before the Senate. Plegis soon fell into an alcohol-induced sleep, which allowed Sidious to attack his master by unleashing four slighting on Plegis' Transparator mask, shorting it out and waking the Sith Lord. Inebreated in half asleep however, Plegis was initially confident he couldn't be killed and was in denial that he was slowly suffocating. Sidious then began to thoroughly mock Plegis and hatefully accused his master of manipulating him into murdering his family, all while slowly torturing and suffocating his master with blasts of lightning. Strangely, Sidious then expressed gratitude to his master for the teachings that Plegis had passed on to him. As the stricken Darth Plegis finally succumbed to death, Sidious felt a monumental shift in the force, which he interpreted as the dark side in joining him as the tool that he used to take over the galaxy.