A mysterious scene depicted a cloaked figure entering a chamber that seemed to include a bacta tank flanked by two Imperial royal guards.
The studio started unveiling promotional materials back in April, when the first teaser trailer was released online.
Longtime Star Wars fans know bacta is a healing substance used in the galaxy far, far away, so theories about who was in the tank flooded the Internet.
Star Wars News Net originally posted the theory, citing evidence seen in a video detailing the creatures and aliens of Rogue One.