The 47-year-old filmmaker is keen for his actors to be "tormented" during shoot but does not want them getting too "villainous", reported E! Online.
"David Ayer is about realism. So if your character is tormented, he wants you to torment yourself. He wants the real thing," Adam Beach, who plays Slipnot, said.
The cast also includes Will Smith as Deadshot, Jared Leto as The Joker, Margot Robbie as Harley Quinn and Cara Delevingne as Enchantress.
Explaining the filmmaker has hired a "life coach" rather than a psychotherapist, Adam said the director is concerned his cast will "disappear" into the "dark side".
"Us actors explore very fine thin lines going to the dark side and he wants to make sure we finish a movie and don't disappear somewhere and then don't show up for work," he said.