Hardening the Steel by Mark B. Gilgam

The Kri are a people of dangerous and cold-hearted mercenaries, on the verge of plunging the northern lands into an abyss of war and destruction. The hero-king Grimwolf leads the united armies into battle in the Bloodswamp, where a generation of warriors loses their lives. The Kri are annihilated there — men, women, old and young, even the children — except for one boy. This is his story.

In the aftermath of that battle, the healer Aslaug discovers the baby lying next to a dying warrior. Having recently lost her two infant sons, she decides to keep it for her own, defying the judgment against his vanquished people. The blacksmith Eckehart helps her keep the secret. They name the boy Kitt.

Kitt grows up on a remote island in the grey northern sea. He works hard to become a master blacksmith, reads many books, and daydreams about faraway lands and glittering cities. He never doubts that he knows everything about his parents - unaware of the dark secret surrounding his birth, and what role King Grimwolf has played.

Warriors from many lands come to Isenkliff to acquire Eckehart's famous Aurora Steel, and they show Kitt how to become a warrior too. Aslaug disapproves of combat and war, and teaches him to heal wounds and harness his growing strength, not to do harm. However, she does not share her knowledge of magic with him.

Kitt faces irate sea rovers, ice-giants, and other monsters. He crosses the sea in an open boat to sail to the Dark Wood Murkowydir, where lost cities sleep, and creatures survive that are long extinct elsewhere. There, the Woodstalkers lurk, who are feared for their stealth and cruelty. The Knights of the Red Lily teach him their code of honour to aid, protect, and serve.