The Ash of War, when applied to melee armaments (excluding daggers, thrusting swords, and whips), imparts the Heavy affinity and introduces the skill:

"Savage Resonance: Unleash a primal roar, invigorating the spirit and augmenting attack strength. During this effect, forceful attacks transform into a series of savage combo strikes."

Discover these war ashes adjacent to the covert village at the valley's base in the northern region of Lake Lienia.

To obtain these battle ashes, engage and defeat the dung beetles in the river beside the divine blessing.