From the Dilapidated Bridge, head toward the cemetery. The shard can be collected from a corpse lying on a segment of floor separated from the cliff and to the right. It is advisable to befriend the giant archer before attempting to get it, though, as the blasts produced by his arrows could send the player into the chasm.
Found on top of a gravestone protruding outside the cliff, in the small graveyard located in front of the cathedral. The area is inhabited by several Infested Corpses. If the player befriended the giant archer in the Undead Settlement, he will lend a hand in clearing this area by shooting arrows.
Inside a small structure found to the right of both the main gate and the Keep Ruinsbonfire. The building is infested by a large group of Rotten Slugs, so clearing the area with ranged attacks is recommended before even attempting to pick up the shard.
Found within the first Skeleton Boulder that rolls up and down the big staircase. In order to obtain the shard, the player must first kill the hooded skeleton controlling it; the boulder will keep rolling one last time and release the shard upon crashing onto a wall and breaking apart.
Found in the long hallway inhabited by two Demon Clerics after coming from the Demon Ruinsbonfire. The shard can be obtained from a corpse lying at the far end corner of this hallway. Special care must be taken before looting the corpse, though, as a Writhing Rotten Flesh will attempt to fall from the ceiling and onto the player if not dealt with first.
Found outside the Church of Yorshka, behind a large tombstone guarded by a red-eyed Corvian. If the player aided Sirris in defeating Creighton at the beginning of the level, he will invade as a dark spirit in this area.
The shard can be looted from a corpse sitting on a chair on a ledge above the area with four Scholars on the sixth floor of the library. This ledge can only be reached by entering through a broken window accessible after coming from the roofs section.
After the Estus Flask has been reinforced for the tenth time, any Undead Bone Shards collected afterward (starting from NG+ and beyond) will have no further use whatsoever, as they cannot even be sold.