The Rule of Unison was the rule created by the Unknown Human Sith that stated for Sith in the Sith Order to not betray each other even in quest for power. It stated that all Sith must be joined together and care for one another. This rule was at first ignored but later due to the workings of certain Sith, was put into effect. The rule was not used after the creation of the Empire and was considered disbanded when the battle on Korriban occured.