After following in the footsteps of the demon- and monster-hunting brothers Sam (Jared Padalecki) and Dean Winchester (Jensen Ackles), the CW wants to make sure that its final night airing new episodes of is as much about the as it is the destination.

To that end, the series finale Thursday, November 19 will be accompanied by a retrospective special,

, which traces the journey the show has taken from its inception to its end and answers some questions fans have always harbored about the show's inner workings, such as how come it took so long for a series about battling demons to introduce its first angel? 

In a preview clip provided to , Eric Kripke, who created the show and served as showrunner for its first five seasons, explains why he instituted a "no angels" policy throughout the show's first three seasons, and also how he came to eventually break that policy.

"I thought it'd be too easy if someone could come in and save them," Kripke said. There wouldn't be much tension in the brothers' ongoing battle with all manner of demons in audiences knew they had an entire heavenly host of 

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