Esfandiyar
Esfandiar or Esfandyar is an Iranian legendary hero. He was the son and the crown prince of the Kayanian King Goshtasp (or Wishtasp). Esfandyar is a name of Avestan (Spantoata) and Old Persian (Spentodata) origin which means “Sacred Creature”. He is best known through the tragic story of the battle between Rostam and Esfandyar, told in Ferdowsi’s epic Shahnameh, or Book of Kings. Esfandyar who was invulnerable and a supporter of the Zoroastrian faith had to fight against Rostam. Both Rostam and Esfandyar share a hero's journey called "Seven Labours" (notice the similarity to 12 Labours of Hercules ). Rostam could defeat Esfandyar only with a trick that he learned from the Simurgh. Esfandyar can be compared to Achilles in Greek or Siegfried in Germanic and Norse mythologies. In Ferdowsi’s Shahnameh, Esfandyar swam in the spring of invincibility as a child, but closed his eyes while swimming. In the story of Rostam and Esfandyar, Rostam learns of this weakness and kills Esfandyar.
The story of Esfandyar's impenetrable skin finds many echoes in legendary stories around the world. We can find parallels in the story of Achilles in Greek Mythology (heel), that of Siegfried in Norse mythology (shoulder), and even India's Mahabharata epic (Duryodhana's thighs).
Esfandyar's vulnerability lay in his eyes, as he closed them while being immersed in the spring that made his skin impeneterable. Similarly, Thetis held her son by his ankle and immersed him in water for the same purpose, thus the Achilles heel. Siegfried's(Sigurd) vulnerable point is a small patch of skin covered with a leaf when he washed himself in dragon Fafnir's blood, and in the case of Duryodhana, his vulnerability occurs when he covers his groins and thighs when receiving the great mystic power of his mothers' eyes .Interestingly enough, both Esfandyar and Achilles died when when an arrow struck them in their respective vulnerable body parts. Siegfried was killed by a spear strike to his vulnerable part, while Duryodhana dies of a mace attack on his vulnerable part.