When the Europeans advanced into the Pure Lands and brought the tools and the influence of the Weaver with them, her minions tried to calcify the native Umbra with new vigor, supported by the buildings of new settlements and railroads. This, in turn, led to violent reactions from the very Wyld-tainted Umbra and its native spirits that soon erupted into violent and unpredictable storms, earning the American Umbra the monicker “Storm Umbra”. The Umbral storms were violent and uncontrollable and grew even worse with the advent of the Storm-Eater. With the consolidation of the Savage West and the re-imprisonment of the Storm-Eater, the Umbral Storms ceased and the native Umbra stabilized into a form that was very similar to the previous known european Umbra, although with more refugees for spirits of the Wyld than Europe would grant.
An Umbral Storm within the Storm Umbra would shatter Moon Bridges, tear down the Gauntlet and create Broken Lands and create havoc, famine and disease among the mortal population, turning them against each other until only Ghost towns remained.