The Great Burn was a disaster that happened in the year 1E 2828. During this time, the Reman Empire was waging a war on Black Marsh that was turning out to be a costly campaign. It was the General in charge of the war whose actions started the fire.
During the Blackwater War of the first era, the Reman Empire continued to suffer greatly in this war that had already lasted for about 17 years. The war was already in its second campaign after General Augurius Bucco was replaced by General Regulus Sardecus and the Imperial Legion was suffering heavy casualties. A new strategy was needed, otherwise the war would be lost.
General Sardecus decided that the Argonians were not the true enemy, it was the swamps and disease of Black Marsh. Sardecus' plan was to destroy all the land. They drained the swamps, salted rice paddies, and cut down hundred, possibly thousands of trees. During the month of Rain's Hand one of Sardecus' most trusted legates, Elisia Mallicius, told some of her sappers to burn a peat bog outside of the city of Stormhold. Little did they know that this bog was part of a massive underground network that led out as far as Gideon and Soulrest. The entire region was set ablaze, and for months the Legion didn't even know about it. This fire would last for over 3 years, and it it would come to be known as the "Great Burn." The inferno of burning peat detritus made the area inhospitable, even for Argonians. The Legion had to give up ground for the first time in years.
The Great Burn may have been one of the most influential moments in the history of Black Marsh. Dozens of Argonian tribes were wiped out, and countless amounts of flora and fauna that were unique to Black Marsh were made extinct by the event. The entire area was nearly uninhabitable for decades to come.
Not only did the native Argonians suffer, but the Legion suffered nearly just as much. Hundreds of soldiers were lost to a disease known as "swamp lung," and hundreds others were killed by gas explosions before they could retreat out of the area. General Sardecus also fell ill and died before he made it back to the Imperial City.