A hellspawn is fictitious creature from the popular comic book Spawn. The main character in the series, Spawn, is himself a hellspawn. The hellspawn are controlled by Malebolgia, the supreme master of Hell, and are mainly used as an officer corps for his army of Hell. Most hellspawns were once human, but were tricked into making a bargain with Malebolgia after arriving in Hell. He would agree to return them to Earth, if they promise to return later on and become a Lieutenant in his army of Hell.
Jo reveals to the Sam possessed Meg that her father and John were in California at Devil's Gate Reservoir, where they set a trap for some kind of hellspawn. John hid and waited, while Bill Harvelle acted as bait.
"Sam" tells Jo that her father was all clawed up holding his insides, forcing John to put him "out of his misery."