The character is the third to wear the mantle of the demonic, cult comic hero, who dates back decades in Marvel and other books. According to the comics, he made a deal with the devil that transforms him into a burning, living symbol of vengeance against evil so that he can avenge a horrible attack on his family.
Luna told ABC News that he's having a blast letting loose.
"It's an animal quality. He's always growling. You can see it written across all the comic panels. 'Grrrr!' He's an animal. The car growls, he growls. He's got this beast inside him," he said.
Luna, whose brother was a huge fan of the character for years, said it was also important to him to represent Reyes as a Latino.
"Boy, that's a great honor. ... I think it's true that he is the first Mexican-American superhero in the MCU," Luna said of the Marvel Cinematic Universe. "And that's just perfect, man. It's a good time for that."
"Agents of S.H.I.E.L.D." returns at 10 p.m. ET on ABC.