Greg is a warrior defined by his physically trained body and a deep-seated desire for vengeance, stemming from the murder of his wife and daughter in the capital. This tragedy fuels his singular drive to fight, causing him to reject guild work and seek direct confrontation with the Black Army. He joins the Volunteer Army specifically to engage these forces. Greg wields a blade in combat, utilizing the skill "Vengeful Blade" – a charging cry followed by an attack dealing moderate damage to a single enemy ahead.

His "Revenge" ability activates for a limited duration after an ally falls, significantly boosting his attack power. He also provides a minor defensive synergy boost through his chain ability. Statistically, Greg begins with moderate health and attack power at lower levels, with both attributes increasing as he gains experience.

Beyond the central narrative, Greg features in various side quests and event stories. He notably appears in "The Queen's Ascension" side story. He also participates in lighter events, such as a comedic scenario where he, Roberta, Cervantes, and Beatrix test alcohol to understand its motivational effects on their comrades; Greg becomes heavily intoxicated after consuming just one drink.

Throughout all his appearances, Greg remains consistently characterized by his tragic past and unwavering focus on seeking retribution against those responsible for his family's death.