While Vulpix and Ninetales might not be the first names that come to your mind when you think Pokémon, they have been here from the beginning and we love them. That being said, if you have a Vulpix, you might not know how to evolve them. Here is how to evolve Vulpix into Ninetales in Pokémon Legends: Arceus.
The only way to evolve Vulpix into Ninetales in Pokémon Legends: Arceus is to give them the proper elemental stone they need. For normal Vulpix, this is a Fire Stone. Alolan Vulpix, which can only be got through a Request, will need an Ice Stone to evolve.
To get either a Fire Stone or an Ice Stone, you can purchase one by talking to the Trading Outpost woman in Jubilife Village. You can buy one of either stone for 1,000 Merit Points which you accumulate by finding Lost Satchels.
Additionally, you can also get evolution stones by riding Ursaluna. After you unlock them as a ride in the main story progression, have them search and dig for rare items. This process is definitely very luck-based, but you can fill up on plenty of nice items doing this.
Finally, you can go to Cobalt Coastlands and into the Molten Arena area to the northeast. Travel around this volcanic area and destroy the clusters of gems for a chance for a Fire Stone to drop. For the Ice Stone, travel to the Alabaster Icelands.
