Thralls

A Thrall is an undead that has been made by a Vampire, Vampires crave souls as a longing of their own soul which is lost.
A Vampire will sometimes persuade a mortal to give up their soul in a ritual, in the ritual, the vampire drains the blood and soul from a willing mortal, that mortal becomes a Thrall and the vampire is rejuvenated for a time by the blood and soul of their victim, but they cannot keep it, after a year the Soul will pass to Hess.
Once a Thrall is made, in the beginning, they are much like their former living selves with all the sapience of their former life but with increased strength and the promise of immortality. But the longer a creature persists without a soul the more twisted they become, the only difference between a Thrall and a Ghoul is time, given enough time, eventually all Thralls will become Ghouls.
Thralls and Ghouls cannot take the Souls of others like a vampire can, but they are still filled with a longing for a soul which slowly increases, Ghouls feast on the flesh of the living as a way of trying to eat their soul, but it never works so their hunger is endless.