A concept sketch of a giant turtle
Author unknown; found here
Someone discovered that the great shiny brown carapaces hold paint well. At first notorious artists decorated the shells with hastily drawn works of art, which paraded through the streets with the tortoises. Then some enterprising souls began to sell advertising space and soon slogans, political graffiti and indecipherable swirls of paint adorned the massive creatures. By the next time the tortoises enter town - perhaps decades later - their shells are clean again - ready to be painted anew.
Of course, none of this makes the Chelonian church happy. Long ago they observed the regular patterns of migration that the different tortoises follow across the years, decades and centuries. They charted the different confluences of the tortoises and realized that they could use these to determine the will of heaven. What if Ralledan rubs past Karnataka, his mate since long ago, at the Square of Beginnings? Then it is a propitious time for new relationships and for celebrating existing marriages. When ancient Peta faces off any of his younger brothers at the crossroads of Pavilione and Shoreline, battle is an omen in all areas of life. The tortoises are holy, either the scions if the gods or gods themselves.
More mundanely, some tether their carts to hard outcroppings on the giant shells and allow the tortoises to pull their heavy goods across town. This is safe for the lone males, but the females with their young travel in convoy, and a cart that trails too far may be crushed or snapped at by huge jaws. Some choose to make a nomadic life out of these tethers, travelling through Torléda from and to the open lands around.
Few have stayed on for a full migration though. The tortoises wander into far lonely places, far from human habitation. Those who have followed them there come back mad and full of enigmatic hints and obscure predictions. The church calls them prophets and claims that the tortoises have been to the realm of the Endless Wind, their true spiritual home.
Certainly the tortoises are strange, and little is known about their life beyond the lands in which humans live. In Torléda few wonder. They continue their busy lives in the shadows of giant shells.