Steely Dan is one of Dio's paid assassins. He uses The Lovers Stand named after it's Tarot Card.
Steely Dan is one of the many stand users hired by Dio to kill Jotaro and his allies before they reach Egypt. Joseph first meets him when he is disguised as a store clerk. Dan's stand activates first by killing Enya Geil. Upon seeing this, Jotaro punches him and somehow, Joseph feels the same effect as him. The stand had got into Joseph's body very quick. So in order to stop The Lovers, Polnareff and Kakyoin shrink their stands to microscopic size and send them inside Joseph. Meanwhile, Steely Dan and Jotaro walk around town in Pakistan as Steely abuses our hero, such as using him as a bridge, making him scratch his back and even making him steal an expensive bracelet getting store clerks after him. When the Lovers was defeated, it tried to get to Jotaro but he catches it. The Lovers then tries to sneak through a girl at which point Steely Dan prepares to cut open Jotaro. Before he could do anything, he realizes that The Lovers has been tied up by Kakyoin before it left Joseph. Then, Jotaro proceeded to beat up Steely multiple times then sends him flying into a wall. Jotaro leaves a note then leaves him.
Dan's stand, The Lovers, is a microscopic insect. He can enter his victim's head through the ear, and get to the victim's brain. Once there, he will attach itself to the nervous system of the victim, and any pain inflicted on Steely Dan will be inflicted twice as hard on the victim.