It was me
Darth Vader's Master is technically the Emperor when he was a Sith, but when he was training as a Jedi his master was Obi-Wan Kenobi
Darth Plagueis' master's name was the Sith Lord Darth Tenebrous.
Darth Ruin's master has not been revealed yet
Darth Vader's old master was Obi Wan.
It was widely assumed that Palpatine's master was Darth Plagueis.
Darth Zannah trained several apprentices for some period of time - Hetton, Set Harth and Darth Cognus. Hetton and Harth only studied under her very briefly, however, Cognus went on to succeed Zannah as a Lord of the Sith. Cognus spent most of her time in the Darth Bane trilogy as an Ikotchi assasin by the name of The Huntress.
Darth Plageuis was the Palpitine's sith master.
himself ,his master is Darth sidius
darth sidious was the apprentice and darth plagues the wise was the master until sidious killed his master and took on an apprentice of his own, darth maul.
Darth Plagueis's master has never been named or revealed.
Not much is known about Darth Plagueis. One thing I know is that Darth Plagueis's species was a Muun, but no one knows who his master was
Darth Tyranus's master was not Darth Caedus. Caedus was way after Dooku had died. Darth Tyranus's real master was actually Darth Sidious (Chancellor Palpatine)