In The Story of the First Guildmaster, Clevis was a king of D'ni in the ancient past. By the time of his rule, D'ni had been suffering from a famine for two generations. Seeking to alleviate the famine, Guild Master Varsil perfected the Art and presented the king with a granary Age. In a gesture of gratitude, Clevis offered Varsil whatever he wished. But when Varsil asked for the hand of Clevis's daughter, Dania, in marriage, Clevis refused and threw Varsil out of his palace.
The Story of the First Guildmaster is not an historical account. There is no King Clevis in the succession of D'ni kings, and the Art was already well-established by the time the D'ni came to be.