Sethan

The Stand is tethered to Alessi's shadow and copies its outline while adding features of its own, chiefly a round head, a pointed crest, and oversized eyes. Turn the shadow to the side and a savage, jagged beak comes into view. Araki drew its design from the opening of the Tetsujin 28-go anime and from the Nazca geoglyphs, and it stands in for the Egyptian deity Set, the god of storms and ruin. Color versions of the manga render the shadow purple, whereas the anime keeps it black. Like most Stands it has no personality and acts only on its user's wishes.

Sethan is a feeble Stand with virtually nothing in the way of attacks, leaning entirely on an uncanny power to leave its opponent weaker than Alessi, which by itself makes it a dreadful thing to face. Since it mimics Alessi's shadow, it reproduces everything he does and holds, so any weapon in his grip is echoed by the Stand and can strike using the shadow of that weapon. The shadow can even act on its own and rise partway out of a surface to lash at a target.

Its signature effect is age reversal: anyone caught standing in Alessi's shadow rapidly grows younger. A mere split-second of contact left Polnareff as a boy of roughly seven or eight, while a woman in her twenties who lingered for ten seconds was reduced to a helpless fetus doomed to die within minutes once cut off from her mother's womb. A Stand user rewound to before they gained their power, as happened to Jotaro, temporarily loses that Stand. The mind regresses too, erasing knowledge held only in adulthood such as friends' names or how to summon a Stand, and Stands themselves grow younger in form, which can shift their look and strength.

Sethan is the Stand of the assassin Alessi, who uses its age reversal to strip his victims of their strength before finishing them. Its name references the Egyptian god Set, tied to destruction and storms.