There was a lot going on Batman v Superman: Dawn of Justice, so much that the movie almost feels like it had too much. That could explain some of the rough reviews it has received, but everything in it was there to set us up for the coming Justice League films.
Regardless of the film's critical reception, Warner Bros. has released an official deleted scene from the film that gives us a look at what the R rated Directors Cut of the film will contain.
This deleted scene might explain how Lex Luthor knew some of the things that he knew. No official description of this scene was offered, but it's theorized that those black boxes are motherboxes that are putting Lex in contact with Apokolips or the Kryptonian archive.
It has also been suggested that the scene shows us Steppenwolf.
Either way, that's some nasty lookin' goo.