The Merraxen-Sith War was a conflict between the merraxen and the Original Sith. At that time the Sith and merraxen were the two most powerful cultures on Korriban and bitter rivals. The rivalary turned violant when Master Hydroth ordered his troops to attack the Sith. The merraxen likely would have won the war, if it wasn't for infighting that broke out during the war. In the end, Hydroth surrendered to the Sith'ari.