The Festering Fang

Ask the adventurers at the camp for news. Talk to Iris at the Dragonspine Adventurer Camp and ask about the tooth. She will suggest speaking to Orban.

Talk to Orban. He will ask you to gather 50 Starsilver Ore, 3 Strange Teeth, and one Northlander Polearm Prototype.

Collect the materials:

Starsilver Ore can be found all around Dragonspine. Use Elemental Sight to help locate deposits. They respawn every 48 hours.

Strange Teeth can be found at specific locations marked on the map (four available, respawning every 48 hours).

A Northlander Polearm Prototype can be obtained from Weekly Bosses, the Liyue Souvenir Shop, the Frostbearing Tree (level 8), or by completing Spiral Abyss Floor 3, Chamber 3.

Talk to Orban again once you have all the materials.

Obtain a Vitalized Dragontooth. Head to the cave with a strange red core in the center of the marker. Defeat the initial group of Fatui (one Electrohammer Vanguard, one Geochanter Bracer, and one Pyroslinger Bracer). Prioritize the Geochanter to remove shields, then deal with the others. Use Scarlet Quartz for power boosts.

Interact with the strange core.

Defeat more Fatui. You will face a Cryogunner Legionnaire and another Electrohammer Vanguard. Defeat the Cryogunner first with Pyro, then use Pyro and Electro. For the Vanguard, use Cryo on its shield and then Hydro, Cryo, and Pyro.

A second group of Fatui spawns: a Cryogunner and two Geochanters. Defeat the Geochanters first due to their shield buffing, then the Cryogunner.

A third group spawns: one Electrohammer, one Pyroslinger, and one Geochanter. Defeat the Geochanter first, then the Pyroslinger, and finally the Electrohammer.

Interact with the strange core one last time to receive the Vitalized Dragontooth.

Return to Orban at the Dragonspine Adventurer Camp. He will forge a Dragonspine Spear, completing the quest.