Hello here is another Idea
This Idea take place many millennium before canon what if Original Lucifer was Killed and someone else take his place and that person that replace him was the one that take control of the underworld with his Monstrous Charisma this said person come from Berserk verse where the Idea of Evil is dead. But This said person didnt Come Alone he was Followed by the man that made him forgot of his dream more than a man is a Beast of The Abbyss that will devour all in his path untill he get him.
Possibilities
The Story might take place after Guts Kill the Idea of Evil and Was Going to finish Griffith until they were both exciled of there world to the DxDverse
Griffith (Femto, Lucifer) and Guts (Hellhound,666)
AN:
If anyone Liked the Idea please review or PM me
This Idea came after reading the Mad Campione by Bboy46
Recomendation: El Tunel by Ernesto Sábato