The Fire Keeper Soul is a key item in Dark Souls III.

In-Game Description

Soul of a Fire Keeper who is said to have returned from the Abyss.
This Fire Keeper preserves the bonfire, and serves its champion. She is said to have soothed and accepted the dark sigil, which has tainted her soul.
And yet, her soul will one day embed itself in the bosom of another Fire Keeper.



Give the soul to the Fire Keeper in Firelink Shrine, thus allowing her to remove dark sigils contracted after leveling up with Yoel of Londor