The 13 Sovereigns are the 13 strongest being in the Void.
The Lord Of Demise (Axan), the absolute ruler and the former strongest being in the Void, split the power of Chaos and Destruction in the Void into 20 being each. These 20 being then became the 10 Sovereigns and 10 Abominations.
The Lord of Demise (Axan) the told toward the 20 being that they would go fight against each other faction, and the one who gain victory will become his right-hand man.
The Sovereigns and The Abomination fought against each other for millions of years until one of the Sovereigns, The Sovereign of Destruction started an alliance to stop the war