Scary Monster

Scary Monster (スケアリー・モンスター) is an ability featured in Part VII: Steel Ball Run, seen as part of the stand, Scary Monsters (plural). It is named after the David Bowie album Scary Monsters (and Super Creeps). 

Appearance/Personality
It can be debated that Scary Monster is not a true stand but the after effect of the stand Scary Monsters, that it lingered and somehow fused with Diego Brando because of the use of his Turbo Eye. The appearance is based on how much Dio is changing but it always retains a black tail with the words 'Dio' repeatably written on it.

Powers
Morph: Dio is capable of changing his body from that of a human to that of a half-dinosaur, fully fledged or partial part of it. While in his morph status he has an increase stamina, strength, speed and vision along with capable of eating anything. Much like Dio's original vampire form, it far surpasses human limit, but without the sunlight weakening. Transmute: Dio also seems to have the ability to morph other creatures into dinosaurs as well similar to the original Scary Monsters stand, but to a lesser extent. However, he is able to turn his horse into a raptor to bestow it the ability to climb walls and can even turn targets into inanimate dinosaur themed objects like candle-holders.

Hand to Hand: Perhaps the most curious and unique ability of Dio's power. Being bound to his body, Scary Monster allows him to fight in first person against other Stands and physically damage them, whereas normally Stands can be damaged only by other Stands.