Grayarts is an assassin for the organization Chaos Choir, commanded by Gladius. His primary missions involve eliminating specific targets, chiefly Coud Van Giruet, and capturing the Edel Raid Reverie Metherlence. However, possessing only basic knowledge of his targets—their names and Ren's post-Reaction appearance—proves catastrophic. He mistakenly identifies Rowen and Kuea as his targets and confronts them, leading to his defeat. During this encounter, Rowen impersonates Coud to extract information on Grayarts' objectives.

Grayarts operates in combat alongside his Edel Raid partner, Cocovet. Their partnership is defined by a shared motivation to dominate opponents and derive satisfaction from humiliating the defeated, fostering Grayarts' arrogant demeanor stemming from their history of uninterrupted success.

His fate diverges between continuities. In the anime, mission failure results in the deaths of both Grayarts and Cocovet. The manga depicts a harsher punishment: Gladius orders Grayarts' arms severed for his failure. Later, after Gladius is defeated by the protagonists, Grayarts resurfaces with a new light-attribute Edel Raid partner. His arms appear restored, potentially through this new partnership, and he executes Gladius. During this reappearance, Grayarts wears Cocovet's Elemental Stone as a pendant.