What's giving initiative penalty during a battle?
 

During battle I noticed multiple time an initiative penalty I don't understand. I wonder from what is coming this penalty.

All units have this penalty and none unit has special effect and nor special traits explaining this penalty.

Is there some ground battle that give penalty to all troops?

Ok the initiative penalty I quoted was coming from a Black Dragon talent decreasing initiative of enemy units level 1-4. There was Black Dragon in enemy army.