Am reading some very silly books at the moment.
The premise being; group of greek gods guards are jealous that Pandora is picked to guard the box. They decide to show the gods how tuff they are and that they made the wrong choice. They steal the box, open it, with the plan being to put all the demons back in after they escape, to show their superiority. They fail and as punishment the escaped demons, who are too strong to be held by anything but the special box which has disappeared, the escaped demons possess the guards who are banished to earth.
They are immortal and to start with the demons of pain, wrath etc hold control and do much damage, but as time has passed the guards have control and lead an uneasy existance with their demons. For instance, the guard housing pain has to cut himself all the time to 'feed' the demon and maintain control.
It's so very Emo. Of course, all this is solved by the love of the right woman and lots of sex.
I can feel my brain's rotting as I read.