We've had several spoilers released today. Spoilers!
The CW released Jeremy Carver's Inside Supernatural for Episode1,
The CW has released the description for episode 2 (note because this was shot third the description calls it episode 3).
“Form and Void” – (9:00-10:00 p.m. ET) (TV-14, LV) (HDTV)
DEAN AND SAM FACE THEIR OWN BATTLES — Dean (Jensen Ackles) helps Jenna (guest star Laci J. Mailey), the nurse he met after the Darkness fell, get back home safely and then sets off to help Sam (Jared Padalecki) deal with a town infected by a mysterious and deadly gas. However, when Jenna falls into dangerous hands, she calls Dean for help and Sam tells him to go back to her. Unfortunately for Sam, he isn’t able to handle the townspeople turned monsters as easily as he thought. Phil Sgriccia directed the episode written by Andrew Dabb (#1103). Original airdate 10/14/2015.
At EW Jared Gives Details on Supernatural's Impala-Centric Episode. Variety announced Nate Torrence has been cast as Sam's Imaginary Friend in episode 8.
See additional discussion at Supernatural Spoilers for September 25, 2015.