Spoilers ahead for anyone who hasn't seen Rogue One.

Rogue One: A Star Wars Story was all about fan service. That approach worked unsurprisingly well considering that the anthology film currently has well over $920 million world wide and is enjoying both critical and audience acclaim. But holding the Star Wars mythology with this level of deference comes with a risk of using kid gloves when making original films enmeshed within the existing narrative. Case in point: Darth Vader. His best days were thought to be behind him since his most memorable arc occurred in the original trilogy, though the subpar prequel trilogy attempted to humanize the iconic villain. (Star Wars: The Clone Wars pulled this off much more skillfully.)

So when it was announced that the Sith Lord would return for Rogue One, fans were understandably excited to see him back in action. However, early drafts of the film saw him leaning heavily on his imposing presence and intimidating reputation, along with a little heavy breathing and force choking thrown in for good measure. Not the most shocking stuff, at least not until that final scene featuring Vader mowing down a score of nameless Rebel soldiers. But when Yahoo Movies sat down with Rogue One editor John Gilroy, they found out that final scene connecting Rogue One to A New Hope was a last-minute addition.

Here's what Gilroy had to say about that impactful scene:

“What was added — and it was a fantastic add — was the Vader action scene, with him boarding the ship and dispatching all those rebel soldiers. That was something conceptualized a little later.”

Some of the framework of the final sequence that audiences saw in theaters was in place from the beginning: After liberating the Death Star plans from the Imperial archives on Scarif and beaming the data to a Rebel Alliance ship, a hard copy was passed to the waiting hands of Princess Leia, who was being pursued by Vader. Gilroy adds, “As far as I know that was always the plan… the main structure was there."

Then the decision was made to have Vader step up his villainous presence, Gilroy confirms:

 “It was a really great punch in the arm and something I think fans wanted to see."

Good change.

Since the reshoot came after principal production, Daniel Naprous was brought in to play Vader for the climactic scene; Spencer Wilding previously filled out the suit for the meeting between Vader and Ben Mendelsohn’s Orson Krennic, with James Earl Jones providing his iconic voice throughout.

Another last-minute addition was the Easter egg of Vader's homebase and site of his climactic battle with Obi Wan Kenobi earlier on, the volcanic planet Mustafar. Gilroy reveals the decision making that went into keeping this location somewhat hush-hush:

“We had one on for a little while, but what we realized was Star Wars fans — true Star Wars fans — if they saw the name, would know exactly what they were going to see. And we wanted it to be a bit of a surprise, so we decided to not put the title on so Star Wars fans could be surprised along with people who were not initiated to where Mustafar was.”

Are you a "true Star Wars" fan? Be sure to let us know your thoughts in the comments!