The Hero's Spirit is Link.

[retrolinkx]

The Hero's Spirit is an undead (assumed Staflos) specter who helps the Link in Twilight Princess by teaching him hidden sword skills and even songs that he can howl as a wolf.

It is said that this is the version of Link from Ocarina of Time, and Majora's mask, and that he is regretful that he did not teach and pass on these lessons that he learned to people who would come and ask for them after he went back to his childhood, this version of Link wants to make sure he does pass something on and ease his regrets, and so he teaching seven skills to his descendant, who is the Link of Twilight Princess.

Source.

[SERIOUSLY THOUGH]

I always thought it was Link, he knows things that Link would know

EDIT - Changed "Lonk" to "Link"

[BumblebeeCody]

At first I didn't believe nor doubt it. But according to Hyrule Historia it's actually true. I just needed solid evidence. I guess it's true.

Hyrule Historia (Page 118) Wrote:Link is taught secrets by the ghost of the Hero of Time, who is his ancestor. After he was returned to the time of his childhood, he felt regret at leaving behind his role as the Hero."

I don't understand the armour though...

[retrolinkx]

It's based of a Stalfos, since they are downed warriors brought back to life, I don't really understand how he became one though.

[Nuudoru]

(08-07-2012 04:15 AM)retrolinkx Wrote:  It's based of a Stalfos, since they are downed warriors brought back to life, I don't really understand how he became one though.

What I've heard is that he became on on purpose to stay alive to teach someone his sword art. Another I've heard (which seems to be the more canon one) was that he was doomed to be one due to some time in lost forest or something.

[BumblebeeCody]

(08-07-2012 04:15 AM)retrolinkx Wrote:  It's based of a Stalfos, since they are downed warriors brought back to life, I don't really understand how he became one though.

If that's true then it makes sense.
As the "plot" goes:

OoT ends (3 way timeline occurs)
Young Link is sent back after saving Hyrule
Young Link ends up in Termina
Young Link saves Termina
However, isn't seen from again as it's "known/theory" that Young Link; after finishing his journey, get lost in the Lost Woods.
As the "legend(within the game)" goes, anyone lost in the Lost Woods becomes a Stalfos.

So I guess that would explain why he is a Stalfos but not necessary a bad one and would also explain how it is Young Link from OoT/MM.