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.
Lost Lore 
The people of Enroth believed the Silence was caused by the concurrent (though in reality unrelated) Day of Fire.