Benicio Del Toro has been cast in "Guardians of the Galaxy" in a mystery role.

Marvel Studios' "Guardians of the Galaxy" has had a lot of big recent casting news. Last week, Glenn Close was revealed to be playing the head of the Nova Corps and "Doctor Who" actress" Karen Gillan was cast as a villain in the film -- and there's even more news on the way. Deadline reports Benicio Del Toro has signed on to James Gunn's "Guardians of the Galaxy" in a mystery role that's "a character that is built to be part of future Marvel films." Del Toro has signed a deal with Marvel with options for multiple films. Comic fans may recognize Del Toro from another comic book film -- he played Jackie Boy in "Sin City."

Speculation has already begun on the role Del Toro has signed on to play in "Guardians," and some already believe he'll be the actor to fill the Titan-sized boots of Thanos. However, there have been no signs to indicate the role the actor might be playing and what the mystery character might mean for the Marvel Cinematic Universe.

Del Toro joins the already cast Chris Pratt, Zoe Saldana, Dave Bautista, Lee Pace, Michael Rooker, John C. Reilly, Glenn Close and Karen Gillen. Directed by James Gunn, "Guardians of the Galaxy" hits theaters August 1, 2014.