Hisuian Growlithe and Hisuian Arcanine are two of the newest forms added in Pokémon Legends: Arceus. While it's not exactly clear if the Hisui region is an alternate version of Sinnoh or a version from the past, it does add tons of new forms to classic Pokémon. In Pokémon Sun and Moon, Pokémon like Meowth were given regional variants that made them fit in their environment more comfortably. This has been a staple in the series ever since and even Pokémon Legends: Arceus has a handful of its own.
Unlike its Kanto form, Hisuian Growlithe is a Fire and Rock-type Pokémon. It's a Pokémon that is highly vigilant and can be found working together to protect its territory. To complete the Pokédex and unlock the Shiny Charm, trainers will need to capture every Pokémon in the Hisui region. Not only that, but each Pokémon has its own list of research tasks to clear. Achieving 100% in Pokémon Legends: Arceus goes beyond just capturing them all.
To find Hisuian Growlithe, trainers will need to wait until they have access to Cobalt Coastlands. It can be found in the wild in both Windbreak Stand and Veilstone Cape, the spawn rate is pretty low so if it doesn't appear, return back to Jubilife Village to reload the spawns. There's also a chance to encounter an Alpha Growlithe in these areas. Capturing these is much more challenging, but they are the super-sized versions of these Pokémon.
Evolving Hisuian Growlithe Into Hisuian Arcanine in Pokémon Legends: Arceus
Fortunately, the method is the same for evolving Growlithe as it is in the older titles. Giving Hisuian Growlithe a Fire Stone will give it the option to evolve into its next form. There is no additional means or method needed for its evolution. Only a handful of Pokémon in the Hisui region evolve using a Fire Stone, including Eevee changing into a Flareon. Fortunately, there are tons of different ways to get Fire Stones in Pokémon Legends: Arceus.
Fire Stones have the chance to appear in red ore deposits when exploring any of the wild areas. Alternatively, trainers can purchase them from Simona's Trading Post in Jubilife Village for 1,000 Merit Points. These are rewarded to players who return lost satchels that they find while wandering in Pokémon Legends: Arceus. There's also a chance for them to spawn in Space-Time Distortions. Since these appear randomly on the map, finding Fire Stones in this method is a bit more time-consuming.
Pokémon Legends: Arceus is available now on Nintendo Switch.