Almost all the characters listed first appeared in The Amazing Spider-Man with the exception of Kaine and Humbug first appearing in Web of Spider-Man. The Prowler is the oldest character appearing in The Amazing Spider-Man in the 1960s in the Silver Age. Many other anti-heroes were introduced in the 1970s in between the Silver Age and the Bronze Age while Humbug was introduced in the 1980s right around the start of the Modern Age. Kaine is the youngest debuted character while Cardiac is the second youngest. Both Kaine and Cardiac appeared around the 1990s.
The practice may have originated in a Celtic festival, held on 31 October–1 November, to mark the beginning of winter. It was called Samhain in Ireland, Scotland and the Isle of Man, and Calan Gaeaf in Wales, Cornwall and Brittany. The festival is believed to have pre-Christian roots. After the Christianization of Ireland in the 5th century, some of these customs may have been retained in the Christian observance of All Hallows' Eve in that region—which continued to be called Samhain/Calan Gaeaf—blending the traditions of their ancestors with Christian ones. It was seen as a liminal time, when the spirits or fairies (the Aos Sí), and the souls of the dead, could more easily come into our world. It was believed that the Aos Sí needed to be propitiated to ensure that the people and their livestock survived the winter.