First of all, this developed from Twohy's unused idea for Alien 3. Had Vincent Ward not been brought and decided that the space prison idea was awful there would have not been a Riddick series.
The film was originally titled Nightfall and about a female outlaw named Tara Krieg with tribal tattoos and enhancements from her interstellar tribe of barbarians. Imam was named Noah Toth, a member of a technology-based version of Christianity and he had no pilgrims, and he was much more scummy and two-faced (if still fundementally good) as he was on a trip to a moon networked with mines where he could advise discontented workers and keep them working. There was no eclipse, only a two-month day and two-month night, there was no geologist's outpost, only Ancient Ruins and temples and instead of aliens the villains were the ghosts of the creatures who built the ruins trying to defend their homeworld. There was no escape ship, but a distress beacon, and Tara, Carolyn Fry, Jack, Noah Toth (Imam) and Paris were all supposed to make it off the alien world, called "Hades" instead of M6-117. Johns' Morphine addiction, The Cannon-fodder Teens, the Solar Orrery and the Geologist's camp were added by David Twohy.
David Twohy's original draft of the reworked story was different, too. Riddick died at the end instead of Carolyn Fry, There were extended scenes of the boneyard creatures, still alive, as well as them being killed and eaten by the other creatures. Paris and Johns would've survived until near the very end of the film, underground, which would've explained the planet's climate and temperature changes, the way the star-system worked, and the life-cycle of the creatures along with an entire underground ecosystem of Starfish Aliens. Also, the starship would've had a voice and its own personality, being a character in and of itself.