Infinite Research: Combat Studies, Magerunner

Took me way too long to figure out but just in case anyone else was confused about this, the quest requires you to take a specific ability called "Naran's Everdisc" in your artifact weapon's talent tree.

Don't be like me and overstress for overthinking it too much: You DO not have to kill enemies while the skill is active, only have it selected as a talent is enough, you don't even have to use it :D

For any of the combat studies quests, I recommend the Coastal Seaguls along the south coast of Stormheim. They're nicely packed together and make for quick kills. Toss in some Young Direbeaks if you run out of seagulls. They both respawn at a decent rate.