Darth Vader shares more in common with the Death Star than he does with his previous life as Anakin Skywalker. The iconic cyborg suit and skeletal mask make him more machine than man in many senses of the phrase, and just as much a killing machine as the Death Star. But he truly lost his humanity after Empire Strikes Back.
Vader was marooned on Mustafar, the very site where he lost his limbs in a battle with Obi Wan, and the Emperor forbade his disciple from using the Force to survive in Darth Vader #7. The test was meant to reinvigorate Vader’s hate after he let Padme’s handmaidens live. To test Vader’s mettle, the Emperor reduced Vader to his bare essentials to realign him to the dark side.
Vader didn’t disappoint. He already basically personified the soulless death machine Obi Wan warned of in A New Hope. Obi Wan says Vader is hopeless and has no more good in him, as it’s been replaced by metal and hatred. The Emperor wanted to seal Vader’s fate and keep him in that state but Vader still has traces of good in him. But after being ripped limb from limb again, Vader had to get creative and welded spare droid parts to his body. Vader is truly now “more machine than man” as Obi Wan says.
Vader spent the first part of his crawl through Mustafar recalling his vengeful sweep of the planet after the Emperor’s plan of domination was set into place in Revenge of the Sith. It places Vader in the same savage mindset that led him down the path of the Dark Side and to the villain behind that black mask. But rather than dwell on his past decisions, he moves forward by forging himself some new limbs.
His cyborg outfit keeps him alive — while also inflicting pain to strengthen his bond to the Dark Side of the Force — and these droid additions keep him upright in a fight with a Sith assassin. Vader embodies relentlessness in both the films and comics, as shown by his willingness to modify his body to survive. Greg Pak and Raffaele Ienco deftly add in panels of Vader standing in lava, letting his droid limbs melt just so he can get the upper hand on the assassin.
The symbolism here is that Vader has completely lost touch with his humanity and cares nothing for his shell of a body. It is only an instrument he wields to vent his rage. He doesn’t kill the assassin, and may not have the faculties to do so at the moment, but learns through some exposition that the Emperor is building another death machine. Instead of an unreliable disciple that sometimes rejects his teachings, the Emperor likely has the Death Star in mind. While he always lived up to being “more machine than man” in a physical sense, Darth Vader displays that in striving to survive by adding more metal to his body, only to let it burn, is a smart metaphor for his renewed commitment to the Dark Side.