The Guidance Stones within the Shrines of the Great Plateau region are used to give Link access to the Remote Bomb, Magnesis, Stasis and Cryonis Runes. Within the Sheikah Towers, their purpose is to unveil each regional map of Hyrule with data on the Sheikah Slate. Once the Guidance Stone is used and the tower is activated, Link can warp back to the tower at a moment's notice. If Link can activate a second Tower, he will earn the Sheikah Sensor. Spoiler warning: Spoilers end here.