Gus Grav, a Subterra-attribute brawler, operates as a pivotal figure within the antagonistic Vexos under the Vestal royal family. His allegiance crystallizes around Spectra Phantom—addressed as "Master Spectra"—after a tournament defeat shatters his solo career, binding him to Spectra even as both desert the Vexos, branded traitors for their rogue ambitions. Sporting long wavy blue hair and green eyes, Gus dons an orange Subterra-marked jacket over standard Vestal garb, brown boots, and fingerless gloves. His personality melds ruthless pragmatism with unyielding loyalty to Spectra, openly scorning ideals like friendship in favor of raw strength. Yet encounters with Dan Kuso and the Resistance slowly erode his rigid philosophy, nudging him toward acknowledging camaraderie’s value. Subterra Rex Vulcan serves as his primary Bakugan partner, augmented by Trap Bakugan Hexados. Strategic upgrades via Chaos Ability X evolve Vulcan into Premo Vulcan and later Rex Vulcan, though Gus discards acquired allies like Aquos Elico and Haos Mega Brontes once deemed ineffective. Key arcs trace his psychological manipulation of Dan, tactical victories underscoring his cunning, and defeats revealing chinks in his armor—notably a rematch overturned by Shun Kazami’s interference. A defining clash with Mira Fermin, Spectra’s sister, forces Spectra to unmask as Keith Fermin, spotlighting Gus’s dual role as enforcer of Spectra’s secrets and reluctant participant in shifting loyalties. Imprisoned alongside Prince Hydron after a failed assault on King Zenoheld, Gus engineers their escape by exploiting Hydron’s paternal resentment, forging a fragile coalition with the Resistance to dismantle Zenoheld’s Alternative Weapon System. Post-war, he rejoins Spectra on Vestal, later resurfacing in Chaos Bakugan conflicts despite his evolving principles. His growth pivots on transitioning from viewing Bakugan as disposable tools to valuing their bonds, catalyzed by losses like Hexados and Blast Elico in battle. A final sacrifice of Bakugan to shield Spectra against Zenoheld cements his complex loyalty—rooted not in power alone, but in layered, hard-won conviction.