Transforming into the dinosaur Utahraptor; Diego gains stripes spelling out "DIO" all over his body. His hair turns into spikes that end in round, ball-shaped tips on the back of his head. Traces of his checkered shirt are still visible on his chest.
After being under the influence of the Stand for a while, Diego is able to turn into a more human-shaped form while still retaining sharp teeth, claws, dinosaur legs and a tail, with a deranged, mad expression on his face.
As the Stand is bound to Diego's body, its appearance is based on the form he takes.
- Infection: Scary Monsters demonstrates the ability to infect other living beings with a virus which transforms them into dinosaurs and also causes them to fall under the direct orders of the user. Each infected person or animal has a different look and capabilities, as well as the ability to infect others with the virus by biting or scratching them. The Stand seems to have no limits in terms of range or number of individuals infected. However, should the user be severely injured, his powers will disappear and all dinosaurs will revert to their original form. The original user, Dr. Ferdinand, was unable to use his Stand to infect his body and become a dinosaur himself, probably because of his deep hate towards these creatures. Still, he can exploit his subordinates' power to travel, either by riding them or by getting swallowed and lying in the body of one of the dinosaurs.
- Diego typically uses this ability to create armies of miniature carnivorous raptors out of birds, rats or fleas, or turn his own horse into one to grant it the ability to climb walls.
- Morph: Unlike Ferdinand, Diego is capable of changing his body from that of a human to that of a half-dinosaur, fully fledged or partial form of it. While in his morph status he has an increased stamina, strength, speed and vision along with being capable of eating anything. It far surpasses human limits similar to the vampires of previous parts, but without the weakness to sunlight.
- Fossilize: Introduced later in the story, Diego demonstrates the ability to not only turn other beings into dinosaurs but, if he wishes to do so, alter them into a hardened dormant state much like a fossil. The ability can be used a variety of ways, from fusing a being into a structure like a rock or tree as a camouflage (not unlike the dormant state of the Pillar Men) to shaping the fossilized being into something more creative like candle holders.
- Hand to Hand: Perhaps the most curious and unique ability of Dio's power. Being bound to his body, Scary Monsters allows him to fight in first person against other Stands and physically damage them, whereas normally Stands can be damaged only by other Stands.