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Signature spider Naegarch drops this. He is in Rath Teraig in Ered Luin. He is a static spawn, not random like some other mobs, so a very good mob to farm for the shards. Note that, no matter your level, when you pull him, every spider nearby will aggro with him. Even as a 38 captain with a 12% chance to parry and 9.5% chance to evade, they managed to knock off a couple hundred morale in between damage and the spider web slow.