While conquering the lands called the Deathlands (which later came to be known as Hammerfell), the Yokudans made no secret of their own self-proclaimed greatness. We should be cautious not to mistake such self-mythologizing for actual history, however.
Whatever their claims to greatness, it is apparent from the record that the Yokudans were brutal and thorough in their suppression of local peoples, leaving little more than blood and bones as a testament to the civilizations that preceded them.
It is no wonder then that the Redguard "civilization" still bears the marks of that brutality to this day.
No greater symbol of the Ra Gada's brutality was the self-proclaimed Emperor Tarish-Zi. His followers proclaimed him as deathless. Indeed, he seemed to be born out of Oblivion, so bloody-minded was he.
It's said that his crypt is still located in Craglorn, venerated by his barbaric descendents.