Grendel: Red, White, and Black
This story is narrated by the adult Stacy Palumbo while she is in an insane asylum. She says that the Dire-Imp (described by her as a Li'l Devil) possessed Hunter Rose, who "had a bright and beautiful capacity but a soul that was quite empty and vast," and corrupted him. The Imp watched and influenced Hunter throughout his life, from the boredom of his childhood, to the tragedy of the death of his lover Jocasta, to his career as a criminal wearing the mask of Grendel. Stacy planned Hunter's death, ruining the devil's plans, but she grew up under its influence as well.
Behold the Devil
The Dire-Imp is a demon from hell that is attracted to Hunter Rose's misdeeds. It follows him around for a few weeks, watching him and reveling in his violence. Although it is invisible, Hunter can sense its presence, but is otherwise mystified. Hunter's confusion leads to him feeling worried and unsure of himself for the first time in his life, and he starts to make a few mistakes in his criminal dealings.
Finally Hunter finds its bloody footprint in the aftermath of an explosion and has a sense of what is going on. He seeks out the services of Toro, a voodoo master, who tells him how to make a magic circle to entrap his own hunter. Hunter kills a group of gangsters and makes the circle with their blood and summons the devil. It appears, unwillingly, angry that it must appear in the corporeal world. It speaks obscenely, throwing out curse words practically every other word. It calls Hunter the "Sparkly One," and "the lordly one, the one who rules on Earth and would refuse to serve in Hell"--an apparent reference to the Grendel spirit residing in Hunter. It also says he is not the first Grendel.
It tells him that it has followed him since birth and helped orchestrate Jocasta Rose, his early lover. This angers Rose, and he breaks the magic circle, enabling the demon to escape. As it leaves, it pricks him with its poisonous tail, which makes him have a delirious prophetic dream, in which he sees his legacy, the future of Grendel as it inhabits Christine Spar and others, until it becomes the dominate force on the planet under Orion Assante. Rose refuses the truth of this dream but is no longer bothered by the Dire-Imp.
A Dire-Imp, possibly the same as the one that followed Hunter Rose, is seen watching over Petrus Christus, a man said to be a tool of Grendel, hundreds of years later. An abbot who is trying to exorcise Christus sees the imp laying in wait outside. The Imp possesses Christus, and talks as if it is Grendel--presumably lying, as did the Imp of Rose's time. While possessed, he rants about the power of Grendel, and implies that there were others before Hunter Rose: Cramoisy, Bolo, Bonnoir, Glassop, and Hendrick. However, these are the names of real-life exorcism victims, so possibly they were possessed by other spirits, or Imps, besides Grendel.
The Imp's power alters Christus' body, obscenely changing its proportions and eventually turning him into a giant mass of skinless muscles. He tortures his attempted exorcist, abbot Chiesa, through telekinetic means. The Imp seems to eventually leave Christus's body, or at least returns him to normal in a physical sense. It is last seen laughing over the tortured body of the abbot, years later.
Matt Wagner has stated in an interview that the devil in Red, White and Black is the same one as the devil in Behold the Devil, despite their different visual appearances.
In the same interview, he states that while the demon says it influenced Rose's life, it is the spirit of Grendel, and that it may well have been lying the entire time, including when it said that Hunter was not the first Grendel. Similarly, the story in Red, White and Black is told by Stacy Palumbo, and is not necessarily true either.
The Imp in Grendel Tales: Devil's Hammer (which once again looks different from its predecessors) may also be lying when it says that it is Grendel, and there were other Grendels before Rose.