How the boon granted to tithonus trasfered itself to a bane?

Answer 1

Aurora - the goddess of the Dawn - begged Jove to grant her mortal lover Tithonus the gift of eternal life. Jove granted the request, but Aurora had not asked for the gift of eternal youth.

Tithonus got older and older, but could never die: weak, crippled, and blind his life became a painful burden to him.

Tennyson's poem reminds us that the gift of youth is for the young alone, and that this is how it has always been, and even how it should be.