Remembrance of Dragonlord Placidusax, hewn into the Erdtree.
The power of its namesake can be unlocked by the Finger Reader. Alternatively, it can be used to gain a great bounty of runes.
The Dragonlord whose seat lies at the heart of the storm beyond time is said to have been Elden Lord in the age before the Erdtree. Once his god was fled, the lord continued to await its return.
While Remembrances can be duplicated more than once through different Wandering Mausoleums, they can't be traded for a copy of an already obtained item in the same playthrough.