The Non-Canon Expert explains what Darth Sidious saw as his Master Darth Plagueis’s greatest strength, considering his lightsaber abilities, knowledge of the Force, midi-chlorian manipulation, and efforts to bring the Sith Grand Plan to completion.
This is a Legends story for Darth Sidious and Darth Plagueis with information taken from a number of Legends sources, including the novels «Darth Plagueis» by James Luceno, «Darth Bane: Rule of Two» by Drew Karpyshyn, and the Book of Sith.