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
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