Check the Johto region restriction
Only Johto League members count toward the member threshold. Kanto members do not substitute for them. Challenges that specify Johto companions must also be completed with Johto companions.
Rare companion: Larvitar
Larvitar is Pokédex #246 and has the Rare tag. It is listed separately from the legendary companions.
Its challenge lists 25 Johto members and a Hard victory in Ecruteak City, without a tracking gauge, status quota or three-beast capture requirement. Normal is below the required difficulty.
