Daisy plays Kira, a character living on Tatooine with Max Von Sydow's character. Kira is a dusty survivalist tomboy. Sydow is a broken man from the prequel area that has become mostly cyborg. He is not force sensitive and for some reason collects artifacts that we've seen at critical points during the previous films, particularly ones relating to the Jedi and the Sith. Daisy shares his fascination with history, and she is revealed in Act II to be the daughter of Han and Leia. As someone with force sensitivity, she resents the fact that Luke went into exile before he could train her, and she hopes that the search for force-sensitive artifacts could lead her to him. She keeps her identity as a Solo under wraps in order to keep trouble away.Sydow's character examining Vader's helmet: http://i.imgur.com/hjVHT65.jpg; http://i.imgur.com/HAzlSnK.jpg
Sydow's character with Kira: http://i.imgur.com/pInbshX.jpg
Sydow is a sort of mentor to Kira, and apparently his true identity is an Act III revelation that will surprise a lot of people. The contention is that he is an existing character from the prequel films, and the revelation of his identity will shock viewers.
Sydow's character is "not overtly" a villain, but has some sort of Sith connection.
Sydow's "hideout" is a downed AT-AT. Relics of the war are everywhere in the film; there is a real feeling that the entire galaxy is sick of the deadlock.
AT-AT: http://i.imgur.com/cm8eBZS.jpg; http://i.imgur.com/FIxykNK.jpg; http://i.imgur.com/LqlrmBZ.jpg
The blue lightsaber in the above picture is apparently the same one Luke lost on Bespin in Empire. The one holding it is Boyega's character (he wasn't necessarily conceived as black).