Straid of Olaphis is located in Lost Bastille after the Ruin Sentinels near the bridge to Sinner's Rise. Initially he is petrified, surrounded by five rupturing hollows that deal physical damage. Straid will be at the opened jail cell. A Fragrant Branch of Yore is required to cure him. One can be obtained at the bottom of The Gutter, immediately before the fog gate to Black Gulch. After you cure him, he will sell the spells as well as offer you trading Boss soul services.