The new show would build on the world established in 'Grimm,' which ran for six seasons on NBC before ending in 2017.

NBC is going back to its Grimm past: The network is developing a spinoff of the series, which ran for six seasons.

The new project, from writer Melissa Glenn (Zoo, Leverage) and Grimm producers Universal TV and Hazy Mills, would be a continuation of Grimm's world. Building on the mythology of the original series, the spinoff will feature returning favorites along with new characters, new mysteries and new dangers.

Glenn and Hazy Mills principals Sean Hayes and Todd Milliner are executive producing. Jim Kouf and David Greenwalt, two of Grimm's three co-creators (along with Stephen Carpenter), will serve as consulting producers.

Grimm debuted on NBC in 2011 and ran for six seasons, proving to be a reliable performer on Friday nights for most of its run. The original series starred David Giuntoli as a homicide detective who discovers he's descended from Grimms, a line of guardians who protect humanity from mythical creatures known as Wesen.

The series also starred Russell Hornsby, Bitsie Tulloch, Silas Weir Mitchell, Sasha Roiz, Bree Turner and Claire Coffee.

The Grimm spinoff joins a show about a basketball coach from LeBron James, the legal drama Adversaries and an untitled cop show from Rosewood's Todd Harthan and Evan Bleiweiss on NBC's drama development slate.