The CW drama's latest run will see former Supernatural producer Jeremy Carver replace Sera Gamble as showrunner.
"Jeremy gave us a couple of years on the show [between 2009 and 2010], so I do think this season will be a little less earnest," Singer told TV Guide. "[It will be] a little more the kind of stuff we did in seasons two and three, before the weight of all the mythology got us."
Singer explained that season eight will again focus on angels and demons, adding that prophet Kevin Tran (Osric Chau) is "an integral part of the year".
"It's not apocalyptic but [the episodes are] about who can gain control and keep demons in hell or angels in heaven," he said.
"Every year we start with a theme - this is our Raiders of the Lost Ark year. This season-long story will be a quest. It's about Kevin and the tablets and the Word of God."
It was recently revealed that Sam (Jared Padalecki) will get a recurring love interest in the new season of Supernatural.
The series returns to The CW on Wednesday, October 3 at 9/8c. In the UK, the show airs on Sky Living.
> Supernatural actor Rick Worthy hints at season eight return
Watch a clip from the Supernatural season seven finale below: