I know Overqwil is available in the Indigo Disk, but I can only find Hisuian Qwilfish in the Polar Biome. Strong style doesn't exist in this game, so how do I evolve it?
Level up your Qwilfish while it knows Barb Barrage.
Overqwil can also be found in 6 star Tera Raids.
Source: Experience. Thanks for reminding me to evolve my Qwilfish!