No I think you're the one misunderstanding the situation, the horn is not like the sword. Ban's comment is just there to inform us that it was indeed a Goddess who was talking to him back then, and that also came in before Death pierce explained that it was indeed a Goddess. It doesn't actually mean that the Goddess is sealed in the horn, nor that she's sealed in the sword either, rather she could have chosen to manifest in the sword until the time came for her to possess Denzel, which from the looks of it isn't now. Basically it's an intermediate state, a temporary vessel for her, since Denzel's sword is blessed by the druids. The druids are the closest to the Goddess and they worship her so they should know a great deal about summoning a Goddess.
It makes little to no sense for the Goddesses to be sealed in objects scattered around Britannia. Who could have enough time and power to do such a thing? See it makes no sense. Cernunnos is the horned god, he is a Pagan God. I already explained in the Goddess thread, that the Goddess clan represent the Pagan gods, while the demons represent Christianity because of the 10 commandments.Pagans are all about revering nature, and the Goddess clan are just that.
So Cernunnos is a Pagan God, just like the Goddesses, so he would actually be on their side, or their ally. Especially now since they're using his horn, and it's unlikely they'd do so if they were enemies at some point.
Of course all this wouldn't matter if it turns out that the demons actually broke from the Goddess clan, and that the demon king was a former Goddess who wanted to be God (hence the 10 commandments) and established the demon clan. Given the ressemblance between the Goddesses and the Gray demons, I think it's more than likely that it is the case. And the Goddess clan seem to be more varied than we have thought
They even have males apparently, or some of them are really flat chested.And the one with the dark wings wears a mask that looks so much like the gray demon's mask.