When Arthur defeated Mammon, he never expected Lucifer to awaken, and what's more, she's made Arthur an offer he can't refuse. Join her in the fight against the Darkness or face the consequences. 
On one hand, it's a good deal. On the other, well, it's Lucifer. 
Worse, she's not the only one who woke up. 
Wrath has broken free. Envy is insane. And Lust? Well, Lust is just looking for a big strong man to… well, you know. To Death. 
Still, if there's one thing Arthur's gotten good at, it's dealing with cranky Archangels. There's just one problem. Heaven's about to fall, and when it does, the Darkness's champion will march on Hell. 
Guess Arthur better fix his sword. Fast.