Nehor appears in the Book of Mormon Alma chapter 1 in verses 2-15.
Being a "large" man of stature Nehor was taken to the Judges in the first year of the reign of the judges (approx 91 b.c.). Nehor utilized his strength and size to intimidate those he preached to claiming that teachers and preachers should be popular and be wholly supported by the people (Alma 1:3).
In his sermons Nehor taught that all mankind will be saved. He declared, "For the Lord had created all men, and had also redeemed all men; and, in the end, all men should have eternal life." (Alma 1:4) Because of his teachings Nehor started to have many followers who supported him financially allowing him to buy many expensive things (Alma 1:5-6).
In his travels Nehor met Gideon, "an instrument in the hands of God", who contended with Nehor of the things with God. But because Gideon was an elderly man Nehor was able to slay Gideon by the sword (Alma 1:9). Nehor was then taken to Alma and was accused of priestcrafts. Nephi, son of Lehi defined priestcraft as "men preach and set themselves up for a light unto the world, that they may get gain and praise of the world; but they seek not the welfare of Zion" (2 Nephi 26:29).
As a result of his action Nehor was sentenced to death "according to the law which has been given us by Mosiah, our last king." It was when Nehor was taken up the hill Manti that Nehor confessed his sins and what he had taught was contradictory to the word of God. It was on the hill Manti that Nehor suffered an "ignominious death" (Alma 1:15).