Collider recently sat down with Arrow showrunner, writer, and executive producer, Marc Guggenheim. In the past, DC has asked Arrow producers to kill off characters that they were planning to use in their movies. For example, Arrow was in the middle of building up their own Suicide Squad, before DC told them to stop because they were making a Suicide Squad movie. Deathstroke is coming back to Arrow in their big Season 6 premiere, and Collider asked how they were able to get him.
“It was a function of… you know, DC control these characters. We went through a period where DC was like, ‘We’ve got plans for Deathstroke that don’t include Arrow.’ That changed at the end of this year,” Guggenheim explained.
Guggenheim went on to say he persuaded DC to let him use Deathstroke in Arrow for a big arc in Season 6, but that they still need to “operate within the requirements of DC”.
Joe Manganiello was cast as Deathstroke for a cameo in Justice League that would set up him playing the main villain in The Batman. Once Ben Affleck stepped down as the director, Matt Reeves came in and said that they’re starting over with a brand new script. It’s very possible that fans will no longer be seeing Joe Mangangiello as Deathstroke in Justice League or The Batman, and that’s why DC has allowed the character to come back to Arrow.
Over the summer, Manganiello told The Hollywood Reporter that he knows what DC’s plans are for his Deathstroke, but he wasn’t able to share them.