Talk to Tanith, choose Yes and come to the Sites of Grace - Audience Pathway.

Pass through the fog gate,pick up the props Serpent-Hunter.

Get the Rykard's Great Rune and Remembrance of the Blasphemous after defeating the boss - God-Devouring Serpent and boss - Rykard, Lord of Blasphemy.

God-Devouring Serpent - Elden Ring Raiders / Rykard, Lord of Blasphemy - Elden Ring Raiders

Sites of Grace - Rykard, Lord of Blasphemy.

Return and talk to Tanith, Volcano Manor Proprietress.

Refresh the map.     Come to the Sites of Grace Rykard, Lord of Blasphemy and talk to Tanith, Volcano Manor Proprietress.