The Celtic druids when you make an animal sacrifice, they are able to cast spells by enhancing the units, I do not know if this could be then but here there is no use of that horn, in Norwegian bersakers when they are involved in a battle, their statistics are slightly modified by power buffs, as I have noticed (and I don't know if I'm wrong) with equipment that tends to have the% critc you have more chances to destroy structures and walls, instead with equipment that tends to damage you have more possibilities in killing enemy units