"Magic exists to serve man, and never to rule over him."
In Tevinter, this statement within the Chant of Light never held the same meaning as it did elsewhere. The Chantry there believed it meant that mages could rule, as long as they did not use blood magic. When the clerics of Tevinter altered the Chant to reflect this, the Divine ordered them to change it, and they refused.
Arguments ensued, until in 3:87 Towers when the Tevinter Imperium elected its own Divine -- Valhail, a man from the Tevinter Circle of Magi -- at the Minrathous Cathedral. And in 3:99 Towers, the death of Divine Joyous II was celebrated in Minrathous and declared a holiday. Enraged, the Chantry declared an Exalted March, calling the coming age, the Black Age. Starting in 4:40 black, and lasting for 70 years, was a bloody war on both sides.
In the end, these Exalted Marches -- four in total -- only served to cement the seperation between Minrathous and Val Royeaux. They were brought to an end after the awakening of Andoral and the Fourth Blight. And to this day, the Schism exists between the two. The Divine in Val Royeaux is informally refered to as the "White Divine" and the Divine in Tevinter as the "Black Divine," though referring to them as such within their respective nations is considered heresy. The Imperial Divine is now always drawn from the ranks of the first enchanters and operates as Divine and Grand Enchanter both.