The Cuchai is like that of the pope in Catholicism. He is the executive leader of the Church of the Sicans. He is elected by bishops after the previous Cuchai dies or resigns, and reigns until his own death or resignation.
The Cuchai is the top of the entire Church of the Sicans. He can nominate bishops, fire bishops, construct great temples, begin holy wars, and even force a leader to resign. The Cuchai is the moral vanguard of the church.