"Bad Guy" Trivia

[Urwen]

Originally Posted by Huinesoron

Why does Gurthang need to come back?

hS

Because:

but it will be by the hand of Túrin that finally death and utter defeat will be dealt to Melkor. Túrin will run his black sword Gurthang (Iron of Death) through Melkor's dark heart, thus avenging the Children of Húrin

It's specifically noted that Turin will use Gurthang, rather than some random sword, to finish the job.

That's why.