Priests are special units in Age of Empires III that can be trained at the Church. They can heal all allied units of their own, except for ships. Unlike in previous games, they can no longer convert enemy units.
"Religion was at the core of early colonial life, whether seeking religious freedoms in the New World or making the arduous journey to convert the Native Americans. Priests, pastors, and lay leaders of the various settlements, colonies, and missions sought to give strength to the struggling communities, binding them together through the bond of shared faith.
Though he was never ordained, William Ames’ works made him a prominent theologian in the New World, though he never made it to the colonies. Persecution for non-conformist religious practices sent him to Holland, where he spent many years teaching and writing, dogged by the British sovereignty until he decided that it was time to venture to the New World. He grew sick and died before he could make the trip, but his works were treasured by Protestant colonists in the New World."