Source: Seven Deadly Sins

Books
I. Devil's Sin of Treachery
Chapters: 24+
Updates: Saturday-Sunday

Blurb

(Takes place after the Sins reunite with Diane and King)

Just as Baltra said, the Sins are back together again but a new prediction is on the horizon. When a mysterious girl enters the Boar's Hat to get a quick drink, the last thing they expect is to see a black-haired doppelganger staring back at them. An ancient threat looms on the horizon, one that Meliodas is increasingly aware of.

Welcome to a Holy War people, where death is not very far.