Writing and concept
"Raining Blood" was written by Jeff Hanneman and Kerry King. D. X. Ferris said that "when Hanneman wrote the song, he envisioned a scene from a dark street or bloody back alley", and later went on to say that the song "described a banished soul awakened and hungry for vengeance." The second verse was written by King, who "pick[ed] up on Hanneman's title and in his new direction". The song, along with the rest of Reign in Blood, was recorded in 1986 in Los Angeles, California, with producer Rick Rubin.
Hanneman explained that "it's about a guy who's in Purgatory 'cause he was cast out of Heaven. He's waiting for revenge and wants to fuck that place up." King later said that "the rest of the song explains what happens when he starts fucking people up. The lyrics 'Return to power draws near' is because he's waiting to get strong enough again to overthrow Heaven. And then 'Fall into me, the sky's crimson tears' is everybody's blood flowing into him. So basically, 'Raining Blood' is all the angels' blood falling on him."