The Silence
The Silence is a major event in the history of Enroth. Enrothian history is divided into two important eras: Before the Silence (BS) and After the Silence (AS).
Enroth was colonized by the Ancients, a futuristic race with an interstellar empire. All of their planets and VARNs were connected by teleporter network known as the Web of Worlds. When the Kreegans went to war with the Ancients, they infiltrated and stressed this network until it collapsed. With that, the Ancients could no longer communicate with the planets in their empire. From the perspective of the people of Enroth, this was seen as a great Silence from their rulers. Before the Silence (BS) was known as the Age of Wonders, when the futuristic technology of the Ancients allowed for the creation of powerful artifacts. After the Silence (AS) was a descent into barbarism and conflict. The primary campaigns in Heroes of Might and Magic III take place around 1160-1170 AS.
Day of Fire 
The following is a story written by Bard Tanni, originally available on the official (now-defunct) 3DO website.
This tale is the oldest that I have to tell—a tale of the Silence. The legend of our Fall from the favor of the Ancients and the Silence we have endured ever since.
Years upon years ago, when the Ancients spoke freely to us, great magic was ours to command. There was magic that could build, change, teach and heal. There were the Heavenly Forges that wrought glorious magical artifacts. And there were terrible weapons that none could be trusted to wield.
It is these weapons and men’s folly that legends say brought the Silence and the Fall. It is said that one of these weapons fell into the hands of bandits, who had staged a raid on one of the Ancient armories. They, in turn, were raided by the local authorities of Aliant, a town located west of what is now called the Mire of the Damned in southern Enroth. The weapon was confiscated from the bandits by the Mayor, who held onto it for…safe keeping.
Widely viewed as one of the most wicked men in history, Mayor Alan had not set out to do harm. Although certainly not perfect, he put the people’s needs before his own. He loved his family: his wife Elaine, their son Michael, and daughter Alanna. His children were healthy and happy; Michael was working his way up the ladder of the military while Alanna was the envy of every young woman in the kingdom. Alanna’s beauty, with her father’s raven black hair and her mother’s brilliant blue eyes began many a fight among her suitors.
One dark night Alanna was found murdered outside the council meeting hall. Her grieving father swore vengeance on the murderer. A message came to Alan accusing his fellow council members of the crime. He ordered the five elders arrested for murdering his daughter. Their vehement denials fell upon deaf ears as Alan dispensed with a trial ordered them executed. One of the five elders, Theodore, was caught while the other four escaped. His execution was swift and painful.
The remaining four, Eldan, Andrew, Thomas, and Matthew, fled northeast to Vissias, a country is south of what is now Blackshire, and begged sanctuary. Alan’s forces pursued but were met by the army of the Vissians who stopped them at the border. Alan demanded the "killers" be turned over to him. The Vissians refused. The two sides fell to fighting, and by the end of the day, Alan’s son Michael had fallen in battle.
Blinded by grief and rage, Alan activated the Ancient weapon. The wrath of heaven poured out of the artifact, instantly slaying both armies to a man and filling the land with poison. Fire rained onto the town of Aliant, burned the green fields of Vissias, and wrought ruin for hundreds of miles around. Uninhabitable for centuries, the formerly lush lands of Vissias and Aliant became the vast desert known now as Dragonsand.
The Colonial Government pled with the Ancients for help, but there was no answer. Some say that the Ancients were appalled by the destruction that we wrought upon ourselves and would not speak to us until we became more civilized. Others are not so sure the events are connected, refusing to believe the Ancients would abandon their children so casually. In any even, without their guiding voice, most of the great magic slowly stopped working and the Heavenly Forge that created these powerful artifacts began to break down.
The legends are unclear on the exact date of the Day of Fire, but they are clear on one thing—the date of the awful Silence that followed soon after. A new calendar was formed to mark the dark occasion—a constant reminder of what happened 1,168 years ago.