The growing franchise of Star Wars has expanded the universe and its world so far that it even encompasses games, comic books, and even animated series. The movement also allowed the material from these different platforms to become canon, which not only enriches the lore of Star Wars, but also lets each one potentially dabble in another unwittingly.
Such may be the case for the Darth Vader #2, which was recently released by Marvel. There is a section where Darth Vader touches on the subject of what could actually be the reason for Luke Skywalker's absence, as hinted in Star Wars: The Force Awakens.
Spotted by Mashable, the comic book shows Darth Vader doing Palpatine's bidding of building a Sith lightsaber. To do this, he would need to find, fight, and defeat a Jedi to get the kyber crystal, which can then be turned evil for the Sith's use. After the Order 66, there's hardly any Jedi left. Or so we think.
Vader makes mention of the Barash vow, which could lead him to a still alive Jedi. The Darth Vader comic goes on to discuss exactly what that Barash Vow is, and based on the description, it may hint at the answer we'll get in Star Wars: The Last Jedi:
"Any Jedi pursuing Barash has sworn to refrain from activities related to the order. Complete disengagement from anything but the Force. It is a type of penance. While a Barash-taker would have felt the purge, they would not have allowed themselves to respond to it, or take action of any kind."
This particular kind of vow would fit where Luke was all this time. And it would explain the mystery behind where Luke was and why he had been silent all this time. Perhaps we would get a better explanation in Star Wars: The Last Jedi, but this is definitely a nice theory to consider.
Star Wars: The Last Jedi will be out in theaters on Dec. 13.