The new Avengers: Infinity War trailer shows the true extent of Thanos' menace, but it may also provide the key to his defeat: Gamora. This would a major change to the comics, in which screen sister Nebula is the one who ultimately bring down the Mad Titan. What's going on?

Perhaps the most exciting element of the new Infinity War trailer is the focus on the Guardians of the Galaxy, who are shown interacting with the Avengers. Center-stage is Gamora, who briefs Tony Stark on Thanos's origin. "The entire time I knew him," she tells Stark, "He only ever had one goal: To wipe out half the universe."

RELATED: Avengers: Why Thanos Only Has Two Infinity Stones

It's a chilling statement, setting up a powerful and dramatic trailer. But, curiously, it also reveals just how important Gamora may be to Infinity War's plot. Fans had expected her sister Nebula (who isn't in the trailer at all) to play a central role; instead, it looks as though Gamora could be the key to Thanos's defeat.

Infinity War Is Exploring Gamora's Backstory

Gamora in Avengers Infinity War

Gamora's backstory was revealed in Guardians of the Galaxy Vol. 2. There, fans learned Thanos has a habit of collecting powerful warriors from the worlds he's conquered. These last survivors become his "children," and are brought up in a state of brutal competition. For Gamora and Nebula, that meant being pitted against one another; the loser would have a limb removed, replaced with cybernetics. Nebula, for her part, was frequently the loser. The two sisters developed a fierce relationship, one united by a strange, twisted sense of need and pain.

The Infinity War trailer suggests the Russo brothers are actually going to revisit Gamora's backstory. One scene shows Thanos invading Gamora's homeworld, and claiming her as his daughter; a child's green hand slips around his finger. Given Infinity War is packed with so many characters and concepts, for this flashback to be included definitely feels like it has some importance. Could it be a sign that Gamora is being positioned as a key player?

Gamora's Knowledge of Thanos Could Help

Gamora and Thanos in Avengers Infinity War

In the comics, the key player against Thanos is actually Nebula. She manages to steal the Infinity Gauntlet from him, only to prove even more dangerous than her "father" due to her lack of self-control. Guardians of the Galaxy Vol. 2 seemed to set Nebula up for a major arc in Infinity War, with her dedicating herself to Thanos's destruction. And yet, she's barely been glimpsed in the marketing so far. Karen Gillan has insisted her character's absence "makes sense," and promises that "Daddy issues will be faced."

Related: The Characters Missing From Avengers: Infinity War’s Trailer

It is possible Gamora's greatest contribution will be her knowledge. She understands Thanos's goals and motivations in a way nobody else can; after all, she grew up under his "care." The trailer emphasizes this right from the start, with Gamora's words giving a chilling sense of scale to the drama. But it actually make sense for Zoe Salanda'scharacterr to be more important. While both "sisters" understand Thanos's evil, Gamora is more of a team player. Nebula, in contrast, is a wild card; she's driven by fits of rage, and lacks the self-control to work well in a team. Gamora has had four years with the Guardians to become a hero, and is known as that to general audiences. This would be one change that makes sense.

Of course, this is just a trailer and could be purposely misleading: perhaps Nebula's absence actually hides a central role. What we can say with some certainty about Avengers: Infinity War is that Thanos has certainly underestimated his daughters.

MORE: Infinity War Trailer Promises Thanos’ Most Iconic Moment

Key Release Dates