An Epoch is a period of time in history or a person's life, typically one marked by notable events or particular characteristics.
End of an epoch[]
In I Shall Seal the Heavens, the end of an epoch is signified by a black wind that sweeps through the Mountains and Seas destroying all life, while also giving life. [1]
Length[]
An epoch in I Shall Seal the Heavens is ~ 100,000,000 years.