The Visitor. The Aggran Chronicles, #2

An ordinary Mayan hunter, Ngu, becomes an unlikely gateway between two worlds when a luminous, wingless being appears above his remote mountain village. The probe, Ilsa-C-1985 from impossibly ancient planet Aggra, finds in Ngu, a connection that will change Mayan history and the lives of Aggran colonists. Chosen by Ilsa, Ngu is swept away from the quiet life of his village into the vaulted, round pyramids of Gauchimontones.
When the priests there learn of Ngu's visions and his unique connection with Ilsa, The Visitor from the gods, he is asked to turn his visionary pictures into a written language capable of uniting scattered peoples throughout Meso-America. The leaders understand the power of language, but power breeds jeolousy. Ngu must contend with an embittered priest who nurses a murderous grudge, a banished warrior who becomes a vengeful commander, and a strange otherworldly plague.
As Ilsa's mysteries deepen, Ngu must learn to wield words and visions alike; to translate alien mind pictures, to hold sway over fearful crowds, and to protect those he loves. With each carved symbol, the stakes grow. Will this new language save a planet from its own violence, or hand its people to foreign powers? The answer depends on a hunter who must become a prophet and the Visitor who refuses to be simply worshipped as a god.