His most fearsome attribute is that he destroys and slaughters for no meaning. Never did he wreak havoc for the obsession of war or domination. It is simply the ultimate nature of a demented yet mighty being to devastate and devour as he wills.
Gilles de Rais the vampire had spent centuries gorging on the living ones since his vampiric birth. He single-handedly drove a multitude of species to the edge of extinction, and sent one quarter of Dark Zone's residents to their afterlife. The power-thriving lords finally put aside their own pursuit of Dark Zone domination and joined hands before he became literally invincible, and the coalition managed to put an end to this mightiest vampire of the time.
During the expedition, the archdemon leading the coalition of lords could not but tremble, pointing his shaking finger to Gilles de Rais and instructed the army, "Behold, all of immorality is present there."
Afterwards, the name of the destroyer "Gilles de Rais" itself has become a horror that almost none would dare to speak out, and from some time on, only the title "Abominable One" is remembered by the mortals.