Legends often borrow from each other, and we can see this among different cultures. In Greek mythology, Achilles’ mother dipped him in the River Styx, holding him by his heel, which became his only weak spot. Similarly, in German legend, Siegfried bathed in dragon’s blood, but a leaf stuck to his back, leaving that spot vulnerable. His uncle Hagen later used this weakness to kill him. In Persian mythology, Isfandiyar was bathed in a magical spring, but he closed his eyes, making them his weak spot. Rustam used this knowledge given to him by Simorgh to defeat him.
It is interesting how mankind has always sought immortality. However, it often fell due to its own weaknesses.