Impossible to kill? That made absolutely no sense. Every man was mortal.
"What do you mean, Mother?" Sigmund asked.
She sighed heavily and told him the truth. Alpheus was actually the son of the leader of the extinct Kanta clan. The king tried to kill him as a baby and it did not work. Multiple times he tried to slash him with a sword and the blows always glanced right off of him.
Perplexed, he ended up taking the infant back to the palace with him to look into why this had happened further. A book about the foundation of the Kanta clan mentioned a legend that was so old it had been forgotten even by the Kanta themselves. The clan leader had the protection of the mountain spirits; until a successor was born he could not die.
The king felt there was no other choice than to raise the boy to be utterly useless, never knowing of his heritage. The clan would not be able to revitalize and he would go through life without being any the wiser about his power.