The Ashen Crusade

"And so we laid waste to all that stretched before us. All that did not fall to the storm of flame we called, we did smite with mine Hammer and the blades of my comrades in arms. And after six long years I looked upon all my work and despaired."

Caspar Edelweiss on the Ashen Crusade

Though Karl Graelingard was regarded by historians as a great Emperor, one event blackened his name in the eyes of some, and lent an aura of fear to his otherwise benevolent reputation: the Ashen Crusade.
Following the The War of the Broken Crypt, the Empire was at peace for ten years, during which time a public works and reconstruction campaign was carried out unparallelled in the last two centuries. Karl spent much of this time situated in Carovin, the center of reconstruction, which was considered the de facto capital of the Empire for several years.
Though Carovin was of great political and strategic importance, this led to major issues. For one, the conservative Tyrian factions viewed his favour towards a traditionally cosmopolitan center as un-Tyrian, and complained he was neglecting the Empire's heartland in favour of the non-human periphery. Secondly, the Greatwood, location of a newly refounded Tyrian citadel at Mannheim, presented a difficult logistic dilemma. Open to attack from hostile elves and fey beastmen, supply lines were stretched thin. The last straw was when an imperial caravan including Karl's mother was ambushed near Karthhavn and slain, and open war was declared by the woad elves of Rhynaria along with the remaining beastmen.
With the aid of Caspar Edelweiss, Hammer of Tyr, the Empire devised a coordinated and ruthless counter attack. After a particularly dry summer, detachments of battlemages from Amon summoned curtains of flame on the southern border of the Greatwood  and fanned it with gusts of arcane wind, creating an out-of control wildfire that was continuously fed by magic. Along the Imperial Highway, trenches and firewalls had been created in which were stationed an army of 70,000, many veterans from the War of the Broken Crypt. Gradually, those pockets of woad elves not incinerated fled north, where most were cut down or taken captive. 
Subsequently, a grueling guerilla campaign ensued where the remaining pockets of independent Rhynarian woad elves were crushed by Caspar's forces. It is said that when Caspar saw the endless devastation of the Greatwood, he wept, and on the last day of the campaign, awoke to find his Hammer gone, snatched away by Tyr.