Marvel Comics set up Darth Vader's return in Obi-Wan Kenobi years beforehand, epically foreshadowing his dark revenge in the new Star Wars series. Taking place after Anakin Skywalker's fall to the dark side in Revenge of the Sith, Charles Soule and Giuseppe Camuncoli's Darth Vader comic in 2017 had to have been a large piece of reference material during Obi-Wan Kenobi's production. Featuring the Sith Lord's rage-filled mental state, his relationship with his Inquisitors, and the hidden secrets of his fortress on Mustafar, Star Wars fans should view this Darth Vader comic as required reading alongside Obi-Wan Kenobi (especially due to one scene in particular).
In this Darth Vader series set immediately after the Sith Lord gets off the operating table, the Emperor puts his new apprentice to work hunting down any Jedi who survived Order 66 while also setting Darth Vader on the path to forge his own Sith lightsaber. He's also given command of the Inquisitors who were former Jedi and kidnapped Force-sensitive children the Empire corrupted into dark agents of the Sith. Seeing them as nothing more than tools, Darth Vader forced them to endure an aggressive training regiment (including the removal of limbs to make each of them understand a brutal lesson of loss).
Darth Vader's dark psyche was also revealed in two very big ways as it relates to his unrelenting mission to gain revenge on his old master. Firstly, the series saw the Dark Lord dreaming about reversing his and Obi-Wan's roles during their duel on Mustafar with Vader emerging victorious while Kenobi is burned by lava instead. As such, this comic foreshadows Obi-Wan Kenobi's new duel between Vader and Kenobi on Mapuzo where the Dark Lord burns Obi-Wan in the third episode, finally getting his revenge and making Obi-Wan suffer as he did (though the Jedi master did manage to escape).
Furthermore, Vader forging his Sith lightsaber saw him receiving a vision in the Force where he lets go of his anger, kills the Emperor, and begs Kenobi for forgiveness. However, Darth Vader refuses this path, believing that his immense hate, rage, and pain are all he has left. It also ensures that his revenge on Kenobi would always be his biggest personal vendetta, creating a strong likelihood that they'd meet again before their final duel in A New Hope.
There's no denying that fans' experience watching Obi-Wan Kenobi can be enriched by reading Marvel Comics' Darth Vader series as well. The new foreshadowing and in-depth explorations into the Sith Lord's psyche are masterfully crafted by Soule and Camuncoli, making Darth Vader an even more tragic and darker villain than he was before. It's certainly a piece of Star Wars lore every Darth Vader fan should read, making his return in Obi-Wan Kenobi even better.