Onslaught presents as a hulking, armored silhouette with a broad chest, thick shoulder plates, and a squat, battle-worn profile. The color scheme mixes gunmetal gray with cobalt highlights and subtle crimson accents that trace the edges of armor panels. Textured surface details, rivets, and weathering give the impression of countless campaigns. The figure features articulated limbs and a robust transformation design that shifts from robot to a tank-like siege mode, with retractable weapons and rotating cannons integrated into the arms. Chrome finishes highlight joints, while a stern visor and crest complete the head sculpt, mirroring the era's stoic warrior vibe. Accessories include a shoulder cannon and a detachable blaster for display versatility.

Within the Transformers saga presented in Age of the Primes, Onslaught is more than brute force; he is a meticulous tactician who coordinates his Constructicon unit into disciplined, devastating formations. He believes orderly conquest requires both frontline prowess and strategic manipulation, turning salvage yards into fortresses and heavy armor into moving siege engines. In prime-era conflicts, Onslaught leads expeditions to secure power cores, disrupt enemy supply lines, and protect vulnerable allies through calculated flanking maneuvers. His leadership earns fierce loyalty from his squad, while rival factions view him as a dangerous planner who can turn any terrain into a battlefield. Over successive battles he evolves into a symbol of organized war and uncompromising resolve.