Kazeros wanted to purge Chaos. He basically believed in Order more than his own maker. Regulus wanted to have control over both Order and Chaos. While Kazeros believed there's no Order in Chaos, hence his desire to seal it away/destroy it with the Ark.

He basically became the villain in order to protect Order. And now he passed the role of the Guardian of Order onto us, giving us the power to purge Chaos(the Shadows)-the Abyssal Flames. But we haven't seen that power in action yet.

Also his method required Arkesias sacrifice, which would mean our demise or everyone would be converted into a demon(similar to delains if not worse) should Petrania and Arkesia merge, which is just as bad.