I remember why Hades loved these eurynomoi so much. The slightest cut from their claws caused a wasting disease in mortals. And when these mortals died, they rose again as what the Greeks called vrykolakai- or in TV parlance, zombies.
-- Apollo (chapter 2)

Importance: This is foreshadowing for one of the main personal problems Apollo deals with throughout the novel. Not only does he contract this undead disease early in the novel, but being around the main villain speeds up the process. Furthermore, this establishes why the battle between Tarquin and the legion of New Rome is so terrifying. Many of the ghouls they face are former members of the legion which creates an underlying sense of fear within the camp itself and raises the stakes of the final battle.

If possible, [Zeus’] Roman incarnation, Jupiter, was even more insufferable than his original Greek personality of Zeus. (And, yes, we gods have multiple personalities...
-- Apollo (chapter 4)