Sethan
Sethan is the stand of Alessi featured in Part III: Stardust Crusaders.
Appearance/Personality
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. Sethan has no personality. It represents the Egyptian God Set, related to tornados and storms.
Ability
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 probably in her twenties stood in it for ten seconds and was reverted back into a helpless fetus. The body isn't the only thing that age backwards, but the mind too, making the target forget things they only knew as an adult (like names or how to conjure a stand). However, if the target knew these things as a child he will keep them, but stands also will revert back to childhood, as Sethan also reverts the spirit, 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 that any weapon he holds is also held by his shadow, allowing it to attack the opponent with the shadow of the weapon, able to come out of the surface it's projected upon.
Trivia
Accordingto JOJOVELLER, its design is based on the opening of Tetsujin 28 anime and on Nazca's geoglyphs.
References
