The Adventist Church believes the Roman Catholic Church to be one of the Harlot Women of Revelation 17—Babylon the Great. They teach that the “man of sin” is the Pope. They also teach that the Roman Catholic church changed the sabbath, enacting a “false sabbath” of Sunday which is the (future) mark of the beast.
The SDA Church’s prophetess—Ellen G. White, who they believe was divinely inspired and corrects inaccurate interpretations of scripture—claimed that Satan held a counsel in outer space to conspire how he could use the Roman Catholic Church (and Protestant Churches) to rile people up in regards to the Seventh-Day Adventist Church.