Mordor, easily based off Hell
The imagery of Hell is most popularly affiliated with Dante Alighieri’s Divine Comedy as having nine circles each of which is for a different gravity of sin. While the imagery itself may not be dogmatic, the very concept of Hell has always been taught by the Church since the earliest of days.
Saint John the Baptist spoke of Hell as well as Heaven when he was baptizing people in the Jordan River; he prophesied how Jesus Christ will have a “fan is in his hand, and he will thoroughly cleanse his floor and gather his wheat into the barn; but the chaff he will burn with unquenchable fire” . Here we see the eternity of Hell as the “unquenchable fire” or fire which never goes out, hence everlasting. This is obviously a not so popular subject. We live in a culture that teaches universalism which means that everybody or almost everybody will eventually go to Heaven so long as the person was not a genocidal maniac.
So the question is: “Does God send people to Hell?” No. By a person’s own free will, they have chosen the way of death as the Didache calls it. To go to Hell one must die in a state of mortal sin and that is a sin which is grave, the person knows it is grave and deliberately commits it anyway . The eternal state of the soul in Heaven or Hell is based on where the heart is, meaning whom the soul claims as its master. Even if one mortal sin is committed and the person dies in this state, they go to Hell because not only did they commit a grave act but their heart was in a dark place and chose the prince of darkness as its master instead of God.
Saint John Paul II gets accused of a lot of things by fundamentalist Protestants and ultratraditionalist Catholics, including a false charge of being a universalist. He lamented that “preachers, catechists, teachers . . . no longer have the courage to preach the threat of hell” . That does not sound like a universalist. A universalist would have outright denied the existence of Hell or would have limited it to genocidal tyrants. That clearly is not the case. He was the traditionalist that called out the modernists in the Church for avoiding the subject ironically.
As the jailer asked Saints Paul and Silas, “What must I do to be saved” . The answer is to believe in Jesus Christ as God’s only begotten Son , repent and be baptized , receive His Flesh and Blood in Holy Communion , and so in other words remain in Christ’s body the Church. This is because His graces are sufficiently found only in the Church since it is Christ’s body and spouse instituted by Himself for the salvation of souls and His Holy Spirit is the Sanctifier. The Holy Spirit works mostly through the Sacraments, visible signs of an invisible grace/reality. E.g. we receive the Holy Spirit’s grace in Baptism, then we receive His graces from the priest (who is ordained by the power of the Holy Spirit) through Confession, we receive the Body and Blood of Christ (which were consecrated by the invocation of the Holy Spirit called epiclesis), confirmed by the bishop in Confirmation with the Holy Spirit.
So, without grace nobody can be saved as one is saved by grace . These graces come from the Father and the Son through the Holy Spirit and so if one has rejected the Spirit they have rejected the Father and the Son as well and have placed themselves in mortal sin due to rejecting sanctifying grace. Christ warned about this saying, “But he that shall blaspheme against the Holy Ghost, shall never have forgiveness, but shall be guilty of an everlasting sin” . So to reject the Holy Spirit is to live in mortal sin; that can go from incredulity, to heresy, to apostasy or committing another grave sin. The Second Vatican Council upheld the necessity of belonging to the Church for salvation (either as a member or through desire [conscious or subconscious]) when it stated anybody “knowing that the Catholic Church was made necessary by Christ, would refuse to enter or to remain in it, could not be saved” .
So we must obey the will of God in faith and works to be saved; those who do not go to Hell. Saint Clement I stated, “If we do the will of Christ, we shall obtain rest; but if not, if we neglect his commandments, nothing will rescue us from eternal punishment” . Saint Justin Martyr wrote that Our Lord “will clothe the worthy in immortality; but the wicked, clothed in eternal sensibility, he will commit to the eternal fire, along with the evil demon” . Many other Church Fathers, Church Doctors, popes, theologians and mystics have written on this subject throughout the ages; it is part of Sacred Tradition and Sacred Scripture, the two parts of the sacred deposit of the faith.
 Matthew 3:12
 Catechism of the Catholic Church, n. 1857
 Saint John Paul II. Crossing the Threshold of Hope, p. 18
 Acts 16:30
 1 John 4:15
 John 3:5, Acts 2:38
 John 6:51-57, Matthew 26:26-28, Mark 14:22-24, Luke 22:19-20, 1 Corinthians 11:21-29
 Ephesians 2:8
 Mark 3:29
 Lumen Gentium, n. 14; Ad Gentes, n. 7
 2 Clement 5:5
 First Apology 52