I am not certain, and it is a long shot but it sounds a bit like *A Companion to Wolves*:

> *A Companion to Wolves* is the story of a young nobleman, Isolfr, who is
> chosen to become a *wolfcarl* -- a warrior who is bonded to a fighting
> wolf. Isolfr is deeply drawn to the wolves, and though as his father's
> heir he can refuse the call, he chooses to go. 
> 
> The people of this wintry land depend on the wolfcarls to protect them
> from the threat of trolls and wyverns, though the supernatural
> creatures have not come in force for many years. Men are growing too
> confident. The wolfhalls are small, and the lords give them less
> respect than in former years.  But the winter of Isolfr's bonding, the
> trolls come down from the north in far greater numbers than before,
> and the holding's complaisance gives way to terror in the dark. 
> 
> Isolfr, now bonded to a queen wolf, Viradechtis, must learn where his
> honor lies, and discover the lengths to which he will to go when it,
> and love for his wolf, drive him.
>
> Source: Amazon description of [*A Companion to Wolves*][1]

It could also be *The Elfstones of Shannara*:

> Allanon returns, having spent the intervening years in magical sleep,
> and conscripts Shea's grandson Wil and elven princess Amberle to save
> the world. It seems that long before human history, the elves
> (revealed to be the real thing, not mutant humans) and other good
> faeries locked all the evil faeries, known as Demons, inside the
> Forbidding, using a magic tree called the Ellcrys. Now the Ellcrys is
> dying, and the Demons are beginning to escape. Amberle, as the last of
> the Ellcrys Chosen, must make the journey to the Bloodfire, to
> fertilise one of the tree's seeds. Since Allanon will be busy helping
> the Elves defend their homes from the Demons, he convinces Wil, who
> has inherited the anti-dark magic Elfstones that the Druid gave to
> Shea, that he must protect Amberle on her dangerous trek.
>
> Source: [TV Tropes page on the *Shannara* series](https://tvtropes.org/pmwiki/pmwiki.php/Literature/Shannara)

  [1]: http://www.goodreads.com/book/show/333356.A_Companion_to_Wolves