The story of Christ descending into Hell does not appear in the Gospels. It is only known from apocryphal sources, such as the Gospel of Nicodemus. But there are some verses in the New Testament that may refer to the journey into the underworld: 1 Peter 3:19-20, 1 Peter 4:6, Ephesians 4:9.
The underlying idea is that Christ descended into the realm of the dead to bring the righteous ones to Heaven.
In most depictions of the story Christ holds a standard with cross. Also there often are crushed doors lying on the floor.
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