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Arianism -

Arianism was born from the teachings of Cyrenaic presbyter and priest Arius. Their beliefs were fairly similar to those of the early Church, except they believed Jesus to be lesser than God.

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Arianism -

The idea was officially declared a heresy at the First Council of Nicea in 325 CE. Arius did get some support from Roman emperors, but then Catholicism was introduced as the official religion and Arianism died out.

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Adoptionism -

While its origins date back to the 2nd century, it was not until the 8th century that a Spanish bishop called Elipandus began promoting it. Essentially, Adoptionists believed that Jesus was just a man, who was born without divinity.

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Adoptionism -

But he was rewarded for being sinless through baptism, and consequentially became a (adopted) son of God. The movement was eventually dismissed as heresy and the sect came to an end.

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Novatianism -

Novatians rejected the Catholic Church idea that lapsed Christians (who submitted to Rome's pressure and made a public sacrifice, denouncing their faith) should be allowed back into the Church.

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Novatianism -

The movement was kick-started by Roman priest Novatian, who disagreed with Pope Cornelius and became an antipope. The sect ended up losing strength and died out.

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Docetism -

Docetism believed the Jesus Christ did not have a real human body. Instead, it was all an illusion, an appearance. This is because the human body could be corrupted, so Jesus could never be a mortal man.

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Docetism -

Docetism was one of the first Gnostic sects, dating back to the end of the first century. There's a criticism of their schism in the Bible, too. "This is how you can recognize the Spirit of God: Every spirit that acknowledges that Jesus Christ has come in the flesh is from God, but every spirit that does not acknowledge Jesus is not from God. This is the spirit of the antichrist, which you have heard is coming and even now is already in the world," (John 4:2-3).

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Donatism -

Caecilian was elected bishop of Carthage in the 4th century, and was consecrated by a traditor bishop (traditors were those who handed over the scriptures during the Roman persecution).

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Donatism -

Caecilian was opposed by Majorinus of Carthage and by those who didn't forgive the traditors. Majorinus tried to get their sect recognized by Constantine, but then St. Augustine rose to power and it was all over for the Donatist schism.

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The Encratites -

This sect's name comes from the Greek word for "continence." It can be traced back to the 2nd century and a man named Tatian.

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The Encratites -

The Encratites would not engage in intimacy and they were even opposed to marriage. The Encratites also didn't eat meat nor did they consume alcohol. Theodosius the Great eventually outlawed the sect and they died out.

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The Naassenes -

This Gnostic sect dates back to the 2nd century. The Naassenes claimed that they followed the teachings of Jesus' brother, James the Just.

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The Naassenes -

According to Christian theologian Hippolytus, the Naassenes "celebrated a serpent." Their doctrine was supposedly delivered by Mariamne, a disciple of James the Just.

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Catharism -

Catharism dates back to 11th-century Western Europe. They believed God created the spiritual world and Satan the material world. Salvation would only occur through a baptism-like ritual known as consolamentum.

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Catharism -

The Cathari believed the soul was a genderless angel, condemned by Satan to reincarnate. They did not eat meat or touch members of the opposite gender. The movement was particularly strong in southern France, where you can still find many Cathar castles.

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Bogomilism -

This sect hails from Bulgaria and is more recent, dating back to the 10th century. It believed that God had two sons: Satanael and Michael. Satanael rebelled, came to Earth, and created the human body and the material world. For his part, Michael is the divine one, who created the human soul.

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Bogomilism -

Bogomils were against the display of wealth in churches and embraced a humble lifestyle. They didn't consume alcohol or have intimacy or eat meat. Bogomils opposed priesthood, baptism, and material relics such as crosses. The movement eventually died out in the 16th century. There are still some vestiges, such as this tombstone in Bosnia and Herzegovina.

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The Cainites -

As the name indicates, the Cainites were dedicated to Adam and Eve’s son Cain, who was punished unjustly by God. The Cainites believed that the creation of the world was actually an act of evil, so that humans could not attain the divine.

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The Cainites -

They also believed that Judas Iscariot didn't betray Jesus. Instead, he just followed his orders. If you want to learn more about it, the gnostic text Gospel of Judas contains alleged conversations between Jesus and Judas. As for the sect, they didn't last long during the 2nd century.

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Phibionites -

The Phibionites, also known as Borborites, had some really bizarre rituals of carnal sacramentalism. These would involve the consumption of menstrual blood and semen (i.e. the blood and body of Christ).

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Simonians -

This sect drew their doctrine from Simon Magus (the Magician), who is considered a heretic and was famously challenged by Paul the Apostle in Acts 8:9–24. They were accused of using magic, and were around from the 2nd to the 4th century.

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Montanists -

Also called the "New Prophecy," Montanists could be considered the forerunner of modern Pentecostalism, given their emphasis on the Holy Spirit and in speaking in tongues. They spread the idea that the second coming of Christ was imminent, encouraging asceticism and martyrdom. Montanists were eventually considered heretics and prosecuted.

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Marcionites -

The Marcionites were followers of Marcion of Pontus. He rejected the Jewish God Yahweh, claiming he was not the father of Jesus. In fact, Marcion rejected any Jewish texts (that would become the Old Testament). He believed Paul was the only true apostle, encouraged celibacy, and forbade marriage. And like other Gnostics, he believed Jesus was never human.

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Carpocratians -

Unlike traditional Christians, Carpocrates championed libertinism and believed in reincarnation. The Secret Gospel of Mark, discovered in the 20th century, offers some insight into their beliefs.

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Marcosians -

The Marcosians were led by a teacher named Marcus. They believed in numerology and letter theory. Their theory of numbers was inspired by the Pythagoreans, and they assigned letters to numbers. E.g. "Jesus" corresponds to 888, which is obtained by adding up all 24 letters of the Greek alphabet.

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Valentinians -

Valentinians followed the teachings of Gnostic theologian Valentinus. He believed in an androgynous Primal Being, with both male and female aspects. The Gospel of Truth, written by the Valentinians, offers more insight about their beliefs.

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Basilideans -

The Basilideans were the followers of Basilides of Alexandria. They were dualists and emanationists, meaning matter and spirit were separate and opposing forces. Jesus was a divine being with no physical body, so he could not be crucified. Basilideans believed Jesus swapped positions (and appearance) with Simon of Cyrene, who was crucified in his place.

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Ophites -

The Ophites are named after "snake," and indeed their eucharist included a snake. They believed that the serpent that temped Eve was actually the hero. This is because the creation God wanted to dominate Adam and Eve by withholding them of knowledge.

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Sethians -

The Sethians were big fans of Seth, the third son of Adam and Eve. They wrote the Apocryphon (or "Secret Book") of John. They make reference to an Unknown God, with male and female aspects.

Sources: (Listverse) 

See also: The biggest unanswered questions in the Bible

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