What are the main beliefs held by Latter-day Saints that are contrary to the beliefs of Christianity from at least Nicene Creed 300 AD to 1800 AD?

I know very little about The Church of Jesus Christ of Latter-day Saints other than that in general they reject traditional Christianity, and think only through their new teaching, can people understand the truth, whatever that is. What are the central departures that they take from the gospel message believed by Christians from Nicea up until their time in the early 1800s?