Sauron

You have come to a magnificent temple... but not one of those temples that innocent and pious people go to... In the past Sauron (aka Tar-Mairon) was just Aulë's Maia, but after that he began to serve to the eldest of the Valar - Melkor. Also, in early times, Sauron was named Mairon and was the strongest of the Maiar. Later, in the first era he was a loyal lieutenant of Melkor, but at the end of the first era the latter was expelled. In the Second Age, he decided to continue to follow in the footsteps of his former master. Tar-Mairon had the White Tree cut down and in its place raised a great Temple in which he performed human sacrifices, persecuting those who were still Faithful. He converted many Númenóreans to the worship of Darkness, becoming High Priest of a Melkor cult.