Kevin Borchardt was the first to be casted.
This movie takes its story from more than one Justice League Dark comic. The meat of the story comes from the "In the Dark" storyline, but the rest is taken from the "The Books of Magic" and "The Death of Magic" stories.
Jonny DiDonato prepared for his role by studying split personalities and demonology.
Savannah Mercedes read M.E. Thomas' autobiography "Confessions of a Sociopath" to prepare for her role as Amanda Waller.