Antoni Gaudí is an E-Gene Holder who serves as a combatant for the organization DOGOO as a member of the First Platoon, alongside his partners Geronimo and Cyx. He is a young boy of short stature, characterized by his fair skin, orange eyes, and distinct green spiky hair. When not on a mission, he typically wears the standard orange platoon uniform, which consists of a long-sleeved shirt and pants, switching to a yellow and orange battle suit during combat operations.

Personality-wise, Gaudí is presented as a friendly individual with a somewhat childish and innocent demeanor. He often tries to act cool and tough, such as pretending not to be interested in a photograph of his teammate Shio, though he is genuinely curious. His gullible nature is a notable trait; he can be easily tricked by his platoon partners, Geronimo and Cyx, who frequently tease him. This teasing causes him to become nervous around them, despite his attempts to claim otherwise. Gaudí is also remarkably honest, a quality that his partner Geronimo openly remarks upon. He develops a crush on Shio before ever meeting her in person, though he is initially disappointed because a digitally altered photo gave him an unrealistic expectation of her appearance.

As an E-Gene Holder, Gaudí channels the spirit and abilities of the famous Spanish architect Antoni Gaudí through an AU ball. This connection allows him to manifest an E-Gene Weapon in the form of a gauntlet that resembles the architect's magnum opus, the Sagrada Familia. His primary role in battle is that of support, as his powers are defensive and constructive rather than offensive. He can create barriers, walls, and roads by touching various surfaces, effectively manipulating the environment to protect his allies or alter the flow of combat. This ability is not limited to solid ground; he has demonstrated the capacity to form water barriers on a surface to defend against explosive threats. He frequently uses his power to construct pathways that assist his partner Cyx in maneuvering more easily with her motorcycle. This specific application of his power is said to reflect the real Antoni Gaudí's architectural methods, as the historical figure was known for working from three-dimensional mockups and mental visualizations rather than detailed blueprints. Beyond his E-Gene abilities, Gaudí possesses an incredibly keen sense of smell, which he has used to detect the presence of explosives from a great distance, even amidst a snowstorm.