Achilles was the seventh son of Peleus, one of the greatest of Achaean warriors, and of the sea goddess Thetis (who had been forced by Zeus to marry Peleus after she avoided union with him). Achilles was also the cousin of Ajax and of Patroclus, his "first soulmate". The priest Calchas foretold that without him, Troy would never be taken. Thetis dipped Achilles into the sacred River Styx to render him invulnerable, but held him by the ankle, which wasn't dipped and remained vulnerable. Another account states that his powers came from an amulet, created by "those who called themselves gods", who allegedly "made him who he was", by elevating a mere mortal to divine strength, power, and vitality. Achilles wore the amulet around his ankle. He inherited the ashen spear of his father, who had been polished by Athena and whose spearhead had been forged by Hephaestus, the wedding gift of Cheiron the Centaur to his parents. He also somehow acquired armor and a sword forged by Hephaestus. He was mentored by Old Phoenix