This shard is found inside Wormroot Depths public dungeon. There are stone stairs that lead to the entrance of this dungeon. They start from the nearby main road. Collectible is in the corner of the first larger room you come across. As you go down the first stairs inside Wormroot Depths, turn right and you can notice it easily. Patrols of nearby creatures are rare, and should not worry you at all.
Northwestern Grahtwood, west of Redfur Trading Post settlement and its wayshrine.