NPC: Alexander Qing, Su Zhou (271,148)
Required Materials: Artifact Lvl 102 (6 stars), Blood Stone, Spirit Stone, Nuwa Stone, Nuwa Divine Stone.
First, to upgrade to Legendary Artifact, your Artifact 102 must be a refined artifact. You can use 5x Lvl 3 Artifact Spell to refine Artifact at NPC Alexander Au, Su Zhou (266,144).
After refining, bring Artifact and Spirit Stone to NPC Alexander Qing, Su Zhou (271,148) to awaken Artifact. Artifact after awakening will activate Covenant 1/9.
Use Ivory/ Gold and Blood Stone to upgrade Covenant 1/9 to 9/9.
After Covenant reaches 9/9, you can proceed to Level Up Artifact 6 Stars to 7 Stars. Use Ivory/ Gold and Nuwa Stone to upgrade it.
After upgrading to 7 Stars, your Artifact will become 7 stars and Covenant 1/9.
Continue using Ivory/Gold and Blood Stone to upgrade Covenant to 9/9.
When Artifact reach to Covenant 9/9. You can use Nuwa Divine Stone to Level up Artifact to 8 stars.
After Level Up to 8 Stars. Artifact will be Legendary Artifact and shape will be changed to the new shape.