Sethan (セト神 Seto-shin) is the Stand of Alessi featured in the third part of the JoJo's Bizarre Adventure series, Stardust Crusaders. It manifests itself within Alessi's shadow and takes on the appearance of a humanoid with a bird-like head. Anyone who touches it will be de-aged.
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 crest, and large eyes. If the shadow is sideways, 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 represents the Egyptian God of chaos and storms, Sethan.
Sethan has no personality of its own and only does what its user wills it to.
Sethan is a weak Stand with almost no offensive options, relying on its esoteric power to make its opponent weaker than Alessi. However, this alone makes it a terrifying opponent to face.
Because Sethan takes on the form of Alessi's shadow, it imitates and replicates everything he does and has.
Because of this, any weapon Alessi holds is also held by Sethan, allowing it to attack the opponent with the shadow of the weapon. Moreover, the shadow can move independently from its possessor and even partially stick out of a surface to attack.
Anyone standing in Alessi's shadow will age backward at a rapid speed. Polnareff, who touched it for a split second, ended up as an approximately 7 or 8-year-old child, while Malèna stood in it for ten seconds and was transformed into a helpless fetus that, without the connection to a womb, would have died within minutes. If a Stand user is de-aged to before they acquired their Stand like Jotaro, they will temporarily lose it.
The mind of the target also ages backward, leading their memories to progressively degrade into vague recollections of things they only knew as an adult (like names of friends or how to manifest a Stand).
If the user is knocked out, all the victims it affected will revert back to their original state.
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