Guardians of the Galaxy and Avengers star Karen Gillan admits she didn’t anticipate Nebula’s longevity in the Marvel Cinematic Universe and credits writer-director James Gunn for tapping into the former villain’s deep emotional potential.

“I thought when I signed onto the first Guardians that I was going to shoot for eight days and then die,” Gillan said with a laugh at Fan Expo Canada. “That’s what it was in the script.”

The cyborg assassin, serving her warmonger adoptive father Thanos (Josh Brolin) in Guardians of the Galaxy when attempting to retrieve the coveted Power Stone, grew past her seething hatred for adopted sister Gamora (Zoe Saldana) in Vol. 2 into a recognized member of the Guardians.

That evolution saw Nebula reconcile with Gamora, who ultimately disclosed the location of the near-unfindable Soul Stone to spare Nebula from further torture at Thanos’ hand come Avengers: Infinity War — a move that ultimately resulted in Gamora’s murder, leaving a grieving Nebula to mourn her lost sister.

“The fact that all of this has happened with the character is really surprising but not, because when I did the screen test for Nebula, it was quite an emotional scene between her and Gamora, which never made it — it was a fake scene, so it wasn’t in the movie,” Gillan said.

“Well, it was an emotional scene, but I started crying during it [laughs]. And then James Gunn really responded to that, I remember, and then we felt that we’d found this whole other aspect of a character that could have just been bad, you know?”

Gillan added the inkling of a deeper character was embedded within Nebula, who went from an attack dog antagonist in Guardians of the Galaxy to a more fully-realized character in Vol. 2.

“It’s funny because that’s kind of where she ended up a little bit. So I think that that was always there within the character, it just hadn’t been tapped into yet. And then, eventually, she found her way there,” Gillan said.

“So I kind of knew she had the opportunity to go there and didn’t think that she would, but the fact that she did made me really happy as an actor.”

Nebula, one of the last-surviving central characters to not have been eradicated by Thanos’ Infinity Stone-powered snap that decimated the universe, will next team with Earth’s mightiest heroes to avenge Gamora and seek to finally enact her long-awaited vengeance on her hated father.

Avengers 4 releases May 3, 2019.