If you head left, you can also get a depraved perfumer carmaan ash. But from Elden Ring Items here you're going to head back through the stairs and into the hidden passages and you will reach eventually the Temple of Eiglay where you fight the Godskin Noble. It's quite a journey because you'll have to travel through the entire magma filled Prison Town and reach the other side of the drawbridge. Make sure to raise the drawbridge as well to get access to a grace point so you can save the game before you take on the Godskin Noble.
So head to the Godskin Noble after defeating him, you will get the godskin stitcher and noble presence incantation. Interact with the item on the altar it's called the serpent's amnion. From here travel back to the Volcano Manor. At this point, we can return to Rya and give her the serpent's amnion, and then she talks about being betrayed. We can then return to Tanith and talk to her and she asks if Rya finds out the truth if we will give her a potion to help her forget. But at best site to buy elden ring items the minute we're not going to do anything with this.