“Eternity” is a place. The Maker of heaven and earth dwells there. The essence is not hidden. Heaven and earth and all things made testify of his power and authority.
And we will meet him in judgment: after death, when “the realm of mortality” is followed by the realm of immortality: unto life, or unto eternal destruction. It is your soul:
And whosoever was not found written in the book of life was cast into the lake of fire.
To avoid being cast into the lake of fire, you need your sins forgiven: that is, your transgressions of the laws of the Maker of heaven and earth: your conscience bears testimony.
Learn why you need your sins forgiven and what you must do: read it in the King James Bible, the epistle to the Romans, chapter 1 verse 18 through chapter 4.