An Oath of Moment is an ancient tradition that harkens back to the time of the heroic Space Marine Legions during the Great Crusade and Horus Heresy era in the late 30th and early 31st Millennia. These were solemn promises, often invoked by several witnesses, usually fellow Battle-Brothers, regarding an individual's future actions in regards to a sacred vow or pledge to be carried out no matter the cost. An Oath of Moment was often sworn before going into battle or setting out on a mission and was taken as a reaffirmation of the sacred oaths made to the Emperor of Mankind and a Space Marine's individual Primarch or Legion. A typical Oath of Moment often required at least two persons -- the individual Astartes swearing the oath and a Battle-Brother(s) to offer it and witness it.