Fate: Condemned by the Bulgarian and Byzantine churches. Bogomil leaders were burned at the stake — Basil the Bogomil was burned in Constantinople ~1111 AD under Alexios I Komnenos after a show trial. Communities survived in Bosnia (where they may have been the majority religion) until the Ottoman conquest (~1463 AD), after which many Bosnian Bogomils converted to Islam — possibly the largest mass conversion to Islam in European history.

Priest Bogomil (~940–970 AD) founded a dualist movement in Bulgaria drawing directly on transplanted Paulician communities. The name means ‘dear to God’ (Bog = God, mil = dear) in Slavic. Bogomils taught a mitigated dualism: Satan was the rebellious elder son of God who created the material world; Christ was the obedient younger son sent to liberate souls. They rejected the Orthodox Church as the church of Satan, refused to venerate icons or the cross, rejected the Old Testament (except Psalms and prophets), and practiced rigorous asceticism — no meat, no marriage, no wine. The perfecti (fully initiated) lived as wandering preachers; the credentes (believers) lived ordinary lives but received the spiritual baptism (consolamentum) on their deathbed. This two-tier structure is identical to Catharism — Bogomilism is almost certainly the direct source of the Cathar movement in Western Europe via trade and missionary routes through Dalmatia and northern Italy.

What happens when a group is declared heretical: The process is rarely sudden. It typically begins with episcopal letters condemning a teaching, escalates to synodal condemnation at a regional council, and — after Constantine — can be ratified by an ecumenical council backed by imperial authority. Once condemned: (1) Leaders are excommunicated, exiled, or — in later centuries — handed to secular authorities for execution. (2) Writings are ordered burned; possession becomes a criminal offense. Eusebius records that after Nicaea, Constantine ordered Arian books destroyed under penalty of death. The same logic applied to Gnostic texts — which is why the Nag Hammadi library was buried in a sealed jar around 367 AD, the same year Athanasius’s Easter letter listed the NT canon and ordered non-canonical books removed from churches. (3) Communities are dissolved by force where state power reaches; in regions beyond imperial reach they survive for centuries. (4) Memory is controlled — the only surviving accounts of most heresies are hostile summaries by their opponents (Irenaeus, Tertullian, Epiphanius’s Panarion), meaning we are largely reading prosecution briefs, not the groups’ own self-understanding.