Moloch is a demon with the ability to use mind control on humans, making them love and serve him. He first came to our attention in 1418, where he created havoc in Italy. He was defeated by an order of monks who created a Circle of Kayless to trap in in the pages of a book.
Fortunately for Moloch, that book found it’s way into the possession of Rupert Giles, Watcher and librarian at Sunnydale High. While assisting with a project to scan all books into the computer, Willow accidentally released Moloch into the internet.
With control over the internet, Moloch poses as a school boy, Malcolm, and convinces two Sunnydale High School students, David Kirby and Fritz Siegel as well as a boat load of scientists to help him create a new body robot body for himself.
In return for her services releasing him into the internet, Moloch also contacts Willow, lures her to his lair, an abandoned science facility where his new body is being made, and offers her a place at his side.
Buffy, however, is on the case, and, along with Xander, follows Willow to the facility while computer science teacher, Jenny Calendar recreates the Circle of Kayless through the internet with her techno-pagan group. The spell ejects Moloch from the Internet trapping him inside his new robot body, where Buffy is able to kill him by tricking him into hitting a circuit breaker which explodes and kills him.