Few characters in all of fiction have had their life story told as thoroughly as Anakin Skywalker, but the official Darth Vader timeline still has plenty of gaps in it. Unless one has delved into the extended lore of Star Wars - the novels, the comics, the video games, and more - they likely have little idea what happened to Darth Vader after Revenge of the Sith but before A New Hope, and that alone represents nearly two decades of the Sith Lord’s physical existence.
As any good supplementary material should, Vader’s extended universe content only serves to deepen and expand upon his persona. Some of Vader’s best moments have come off-screen and between movies, and while it’s not required reading in order to appreciate the character, it is necessary if one wants to fully understand him - lest he find your lack of detailed knowledge disturbing.
19 BBY: Vader Defeated Jedi Master Kirak Infil'a So He Could Take His Lightsaber's Kyber Crystal
Immediately following his dismemberment at the hands of Obi-Wan Kenobi on Mustafar, the newly rebranded Darth Vader took some time to adjust to his cybernetic body parts. After asserting his dominance over Vader with a little Force lightning and a threat of decapitation, Darth Sidious took his apprentice to a ceremonial destruction of confiscated Jedi lightsabers and let him in on the secret to constructing a red saber fit for a Sith: One has to take a lightsaber from a Jedi, and then make its kyber crystal “bleed” by pouring their rage and pain into it.
Thus, Vader’s first mission as a Sith Lord was to track down a Jedi and take their kyber crystal through vicious means. He caught wind that Jedi Master Kirak Infil’a, a combat expert, had survived Order 66 and fled to the river moon of Al’doleem, where Vader paid him a visit.
The first clash between the two ended in Vader being blasted down from the top of a mountain, resulting in more severe injuries. The second time around, Vader distracted Infil’a by endangering the lives of several civilians, then stole his weapon and fatally Force-choked him. In the midst of a raging storm, Vader succeeded in pouring enough negative emotion into the blade’s crystal to make it bleed - and that’s how he obtained his soon-to-be iconic red lightsaber.
19 BBY: Vader Eliminated The Jedi Librarian Jocasta Nu
With a Sith lightsaber in hand, Darth Vader began a campaign to carry out Order 66 to its fullest, tracking down any Jedi fortunate enough to escape the initial purge. Conveniently enough, his next quarry, Jedi librarian Jocasta Nu, came to Coruscant hoping to find a record of Force-sensitive youth and keep the child out of the burgeoning Empire’s possession.
At first, Vader - who had known Nu in his previous life - attempted to stop the Grand Inquisitor from slaying her and implored her to join him on the dark side. His stance changed, however, when Nu revealed to an assemblage of clone troopers that had cornered her that Vader was Anakin Skywalker. In response, Vader terminated the troops and then Nu.
Curiously, however, he then destroyed that list of Force-sensitive children, informing Emperor Palpatine that it had been lost along with the librarian.
19 BBY: Vader Took Over The Sith Inquisitorius And Joined Them On Missions To Track Down The Remaining Jedi
As Darth Vader became aware of the Inquisitorius, headed by the Grand Inquisitor and employed by the Emperor, he was less than impressed. Learning that most of the Inquisitors were former Jedi who had turned to the dark side, Vader insisted on taking over their training. His unrelenting methods - which included the dismemberment of his pupils - proved effective, and it wasn’t long before the Inquisitorius was ready to join him in his mission to complete the Jedi purge.
Though some individual Inquisitors would eventually turn on Vader and the Empire, most stayed loyal to their harsh master for years to come.
18 BBY: Vader Survived A Bounty Placed On His Head And Took Out His Rage On His Imperial Rivals
While hunting down a lead on a runaway Jedi, Darth Vader was accosted by a family of bounty hunters. After cruelly dispatching them, he learned of a significant bounty placed on his head - and then had to fend off several more assassination attempts.
At first, Vader suspected the Emperor was behind this and confronted him with the accusation - but Palpatine denied it, informing him he still intended to teach Vader, not test him. After further investigation, Vader determined the plot had actually been sprung by some high-ranking Imperial officers who felt threatened by his sudden appearance and rise to power, but he couldn’t be sure about which officers specifically were involved.
So, Vader had the Emperor call all the elite Imperial officers for a meeting. Then, he called out five of their names at random and Force-choked them viciously in front of their colleagues. Vader announced all future assassination attempts against him would result in five more random executions until he ran out of officers - and the message was received loud and clear.