Sethan is bound to Alessi's shadow, taking its form but with a distinguished shape, the most prominent feature being its round head, a pointed horn and large eyes. If the head turns in profile, the horn is revealed to be a crest, and Sethan's cruel, jagged beak is revealed. Its design is based on the opening of the Tetsujin 28-go anime, as well as the Nazca geoglyphs. Sethan has no personality. It represents the Egyptian God Set, related to tornados and storms.
Age Reversal: Anyone standing in Alessi's shadow will age backwards at a rapid speed. Polnareff, who touched it for a split second, ended up as an approximately 7 or 8 year-old child, while a woman in her twenties stood in it for ten seconds and was reverted back into a helpless fetus. The mind of the target also ages backwards, making them forget things they only knew as an adult (like names or how to conjure a Stand). If the target knew something when they were a child, they will retain that memory. Stands also revert back to childhood, as Sethan also reverts the spirit and not just the age.
Shadow Reflection: As the Stand takes on the form of Alessi's shadow, it imitates and replicates everything he does and has. Because of this, any weapon he holds is also held by his shadow, allowing it to attack the opponent with the shadow of the weapon, which comes out of the surface upon which it is projected.