Ring of keys to the Irithyll dungeon held by the jailer.
Opens most cell doors.
On what grounds do they remain imprisoned, considering that by now they are mindless Hollows, or unrealized, gibbering fools?
Found in the upper levels of the Giant's cell in Irithyll Dungeon. To reach it, traverse through the toxic swamp of the Profaned Capital, up the chapel and through the passage looking over the Giant's cell.