Giantsbane

Eleven years ago, Dunstan Harrowgate's sword snapped in a siege breach, and the younger brother standing at his shoulder died on an enemy pike. He has been trying to become strong enough ever since.
Then a wandering chronicler walks into the Iron Hall and tells the tale of Giantsbane: the dwarf-forged blade of the northern kings, said to give its wielder the strength of the giants it was made to kill. It lies on a dead king's breast beneath Haldrinhold, a castle three hundred years in the hands of a frost giant jarl who sleeps on the greatest treasure in the north.
Dunstan hires a company. A broken army priest with one last act of penance in him. A disgraced mage chasing her murdered mentor's lost spell. A halfling thief with four thousand crowns of debt and a killer on his trail. A half-elf ranger who has hated giants since the night they crushed his father. The gold will be split five ways. The sword is Dunstan's.
But the road north runs through drowned forests and haunted keeps, gnoll war camps and kobold tunnels, barrow downs and troll-infested deeps, and every mile reveals that the legend was a lure. The sword is the key to a prison. Something beneath Haldrinhold has been waiting for a man exactly like Dunstan, and when the jarl's axe falls in the vault and his friends begin to die, he will have to choose what kind of strength he truly came for.
An R-rated epic of fellowship, sacrifice, and hard-won mercy, with a sweeping cast, a slow-burning romance between a ranger and the last elf warden of a murdered realm, and a last stand readers won't forget.