Okay, my army's strengh was above 2500, and I got this, no doubt another bug of the French version. It got me to three endings but none of them seem to be Deal with the Devil.
There is some typo but the problem you describe isn't a bug. I probably wasn't clear enough, so I will try to be as precise as possible this time :
-Do all the character arc in good ending
-Conquer the land to trigger the one for Shakti (but don't complete her story)
-As soon as the angel's army is mentionned make Erius spawn (as he doesn't require for you to complete all arcs, just to control all the lands)
-During Erius questline, it's mentionned that angels powers would have been a great asset to fight him
-If you are on the good road, Xeona will remember the angel army and plan to make her two ennemies fight each other
Do you have a save before Shakti's arc ?