The Bible describes Hell as eternal. Jesus talks about this in Mathew 25:41 “Then He will say to those on His left, ‘Depart from me, you who are cursed, into the eternal fire prepared for the devil and angels.’” In this passage He is telling the parable of the sheep and the goat. This parable describes the end times when God will separate the righteous from the unrighteous.
In Job, which is what we know to be the oldest book in the Bible, we see descriptions of Hell being dark. Job 10: 21-22 “Before I go to the place of no return, to the land of gloom and utter darkness, to the land of deepest night, of utter darkness and disorder, where even the light is like darkness.” among many other verses where Job talks about the afterlife. These verses show how some of the earlies people understood death.
Hell is a torturous place. Mathew 13: 24-30. In this passage Jesus is sharing the parable of the weeds. It talks about a farmer who plants good seeds, and then in the night an enemy goes to plant bad seeds. The farmer lets both seeds grow, and then during harvest he burns the weeds and takes the wheat to his barn. This parable is a clear metaphor for when God separates the righteous from the unrighteous, which Jesus explains in verses 36-43. In verse 41-42 he says “The Son of Man will send out His angels, and they will weed out of His kingdom everything that causes sin and all who do evil. They will throw them into the blazing furnace, where there will be weeping and gnashing of teeth.”
Finally, Hell is an unquenchable fire. Isaiah prophesied about an unquenchable fire in Isaiah 66: 24. “And they will go out and look on the dead bodies of those who rebelled against me; the worms that eat them will not die, the fire that burns them will not be quenched, and they will be loathsome to all mankind.” This verse is the basis of the later Jewish concept of Hell. There are many other examples of the idea of eternal fire in Hell in Mathew.