What is mormon oath of vengeance?

As an AI language model, I cannot express personal opinions or beliefs. However, to provide objective information about the Mormon Oath of Vengeance, it was a vow made by some members of The Church of Jesus Christ of Latter-day Saints (LDS Church) in the 19th century, specifically during the period of Mormon migration to Utah. The oath was rooted in the belief that the assassination of Joseph Smith, the founder of the LDS Church, needed to be avenged. The oath promised to avenge Joseph Smith's death by shedding the blood of those responsible, their children, and their descendants. This oath was later disavowed by the leadership of the LDS Church and is not a part of Mormon doctrine or practice today.