I HAD AN IDEA OF WHAT IMP!GUY COULD BE LIKE
Dunno if he'll be added to my fic. BUT
He's a vampire. He was turned by someone looking to become a Mass Maker who decided to use their local pizza delivery to gain more.
And Guy had been tranced for it, and didn't remember the ordeal. So all he knows is he feels under the weather, and hungrier.
Until one day, he wakes up with blood on his hands. First he's brushing it off as a dry nose bleed and was prepared to make a sauce joke...until he saw what it really was.
Honey, on their shared bed, cold as a corpse...
They are a corpse.
And he realizes, the taste is still there. The metallic thick flavor.
The one person who tolerated his puns, who would smile at his crazy ideas, who would giggle at the stupid little things he'd do, who was his light in this world.
And he killed them. Their blood was on his hand, in his mouth, on his teeth, warming is stomach. He did this.
Now fast forward, a while after his bloodlust subsided. Revenge is a pizza best served cold.
And from what we've seen of vampires, they're seemingly instinctively cold and cruel. So while Guy has become a vampire-hunting vampire, he's fighting to keep his humanity, to keep the memories of his Honey warm and loving in his coldened heart. But the vampirism fucks with his head and his conscious so much.
And if you want to include the headcanon that Angel was his family, his grudges also lie in the great king Damien. Only amplified when Damien is also vampirized.
Him making constant references becomes his way of grounding himself, of remembering the familiar. Him with a fucking sword and before he slices a vampire's head off, he says "Hasta la vista, baby." Or every time he walks into his place, he says "Honey, I'm home." with very little energy. Or he takes a locket out from beneath his shirt, an image of Honey (maybe even Angel, too), before he says "Honey, we've got a big storm comin'," before he heads off to a very bloody night.