Touchstone Glass is located in the city-state of Tharios. It is a glass shop, and is owned by Antonou Tinas, a very skilled glass-worker. It is located on the main road of Tharios heading up to Achaya Square. It is where Kethlun Warder did most of his projects while staying in Tharios, as he was kin to Antonou Tinas. Touchstone Glass only appears in Shatterglass, the fourth and final installment of The Circle Opens quartet.