Catalan dominion in Occitania, which aroused the hostility of the county houses of Baus and Toulouse, ended at the time of the persecution of the Cathar heresy, which preached extremes of spiritual perfection and the adoration of good and evil, while denying the Incarnation. The French nobility joined the crusade, proclaimed by Pope Innocent III, that cruelly razed Occitania. Pere I el Catòlic fought on the side of his vassals and was killed at Muret in 1213. The defeat led to a crisis within the institutions of Catalonia and put an end to the dream of expansion to the north.