Short answers, pulled from the story.
The word heresy began as a neutral term in Ancient Greek meaning simply choice or thing chosen. Early usage described the process where a young person examined various philosophies to determine how to live.
Constantine the Great called the first ecumenical councils to end this doctrinal debate initiated by Arius during his reign over the Roman Empire. He enforced orthodoxy through Imperial authority to ensure domestic tranquility and efficacy of prayers supporting the empire.
Priscillian became the first Christian heretic executed in 386 when condemned by Roman secular officials for sorcery alongside four or five followers. This event occurred after the Edict of Thessalonica issued in AD 380 by Theodosius I made Christianity the state church of the Roman Empire.
Martin Luther was famously excommunicated as a heretic by Pope Leo X through papal bull Decet Romanum Pontificem in 1520. This action marked a significant shift from voluntary selection to pejorative variance with established customs within the Christian community.
Heresy remains an offense punishable by death in some nations today including systematic persecution of Bahá'ís in Iran where their faith is considered an Islamic heresy. This situation follows historical patterns seen since medieval times with charges punishable by death.