Known rulers, in the History of Egypt, for the Twenty-First Dynasty. The Twenty-First, Twenty-Second, Twenty-Third, Twenty-Fourth and Twenty-Fifth Dynasties of ancient Egypt are often combined under the group title, Third Intermediate Period. After the reign of Ramesses III, a long, slow decline of royal power in Egypt followed. The pharaohs of the Twenty-First Dynasty of Egypt ruled from Tanis and were active only in the north of the country. This dynasty was described as 'Tanite'. Meanwhile, the High Priests of Amun at Thebes effectively ruled Middle and Upper Egypt in all but name.