The initial response to Marvel’s Guardians of the Galaxy has been extremely positive, but fans and reviewers alike have noted that the film left viewers with a number of questions which unfortunately may not get answered for years. From unresolved origin stories to mysterious new characters, several elements of the intergalactic superhero film may leave all but the most dedicated of comic book enthusiasts in the dark.

Guardians saw the return of the 8-foot-tall purple space villain Thanos, who was introduced in the Avengers post-credit scene. In this film, Thanos is visited by the film’s primary antagonist Ronan the Accuser, and it is apparent that Ronan is operating as an agent for the Mad Titan in his search for the Infinity Stones.

Fans of the Marvel cinematic universe may not recognize those words, but two Infinity Stones have actually been seen already – the blue all-powerful Tesseract which grants its owner godlike abilities featured in Captain America: The First Avenger and The Avengers and the red Aether seen in Thor: The Dark World are both Stones. The orb in Guardians contains a third Infinity Stone. Thanos, played by Josh Brolin, hopes to assemble all the Stones to form the Infinity Gauntlet, which would make him all-powerful and help him rule the entire galaxy.

However, that doesn’t happen in Guardians, so viewers are left in the dark as to how Thanos’ story will resolve, assuming Marvel decides to continue to develop it. Thanos will likely be featured in 2017’s Guardians of the Galaxy, as both Drax and Gamora have some kind of score to settle with him and the Mad Titan’s story primarily takes place in space. However, there’s also a popular theory that he’ll be the main villain in the third Avengers.

Thanos’ story is far from the only one left unresolved in Guardians – fans still don’t know the complete origin story of Chris Pratt’s Peter Quill, the central character of the film. Star-Lord’s dying mother tells him that his father was an angel, and viewers learn later in the film that his father was an extraterrestrial who sent Yondu and the Ravagers to deliver Peter to him. Peter is able to hold the Purple Infinity Stone, a feat which no mortal man should be capable of, so it seems he is the son of a very ancient, powerful being. Comic fans aren’t even sure where Marvel is going to go with this subplot, as his father wasn’t a particularly remarkable alien in the comic series. This means the studio may intend to retcon Peter’s origins and give him a new, more powerful father figure. Popular fan-theories include The Beyonder and The Stranger, two powerful space-dwelling comic characters.

Writer-director James Gunn, who will also work on the Guardians sequel, has assured fans that he already has the story of Peter Quill’s father mapped out.

The film’s post-credit scene also features Howard the Duck, a 70s superhero who faded into obscurity when an attempt to give him his own feature film failed miserably. Marvel has yet to comment on whether or not his appearance means Howard will be seen in any future films.