Hiemo asks you to bring him a pokémon that has a scythe on each arm.

The Request

After you unlock the ability to ride around on Basculin, go to the Obsidian Fieldlands and use Basculin to ride to the southwest island. Approach Hiemo there to accept this request.

Get a Scyther

Hiemo wants you to bring him a Scyther. They can be found near Grandtree Arena in the Obsidian Fieldlands. Put the Scyther into your party and talk to Hiemo.

Reward

Afterward, you get 1 Seed of Mastery.