I was playing as the daughter of Haraldr Fairhair and had just beaten back the Aztec armies in Britanny ( which I set up as an independent Norse kingdom), when the shepherds crusade fired, with as leader one of the Aztecs who had conquered France before I destroyed their armies (62 martial and picking off stacks can do a lot). the flavour text did say Huitzilopochtli instead of God, but I don't really think it would make sense for the Aztecs to launch a crusade for Jerusalem.