The mage - Inbali Iserles

Full of heart, fantasy, and adventure, the I AM FOX trilogy follows
Isla, a young fox whose world is shattered when her family suddenly
vanishes. Foxfire, the final book in the trilogy, follows Isla
on her continued adventures.
Isla has arrived at the frigid Snowlands to find her lost brother,
Pirie. The tundra is a harsh place - and the wolves who live within
its icy kingdoms are harsher still - but Isla's flair for the
mysterious arts of foxcraft has grown tremendously.
The young fox is on a mission of grave importance. A cruel and powerful
fox known as the Mage is using his own mastery of foxcraft
to summon an ancient threat. If he succeeds, then more than just
Pirie's life will be at stake.
But Isla discovers the once-proud wolves are broken and wary. Their
king is weak, struck by a peculiar madness, and a rival kingdom
threatens their borders. If Isla can't find help amongst the wolves,
then the whole world will burn