Rya is an NPC Introduced in Elden Ring. I am Rya, in the service of Lady ... Talk to her. Here, you have three options. Kill her, give her the Tonic of Forgetfullness, or leave.

Rya’s Necklace is a Key Item in Elden Ring that can be used to progress Rya ... If you kill the Blackguard, his quest is over. Once you have the necklace, bring it back to Rya to continue ...