Final answer:
The satan worshiping killer known as the Night Stalker who terrorized Los Angeles was Richard Ramirez. He was a lone serial killer, different from historical organized vigilante groups, and was sentenced to death. His sentence was upheld across appeals until his death on death row.
Step-by-step explanation:
The satan worshiping killer who terrorized Los Angeles in the early 1980s was known as the Night Stalker. His real name was Richard Ramirez. He was not associated with vigilante groups like the nightriders or groups such as the Ku Klux Klan that emerged in the 1860s and were infamous for their premeditated acts of violence under cover of darkness. Instead, Richard Ramirez operated alone and was eventually caught and convicted for his crimes. His reign of terror caused great fear in Los Angeles, and after his capture, he was tried and sentenced to death. Despite numerous appeals, his death sentence was upheld until he died of natural causes while on death row.