Dragontiarna Series by Jonathan Moeller

Ridmark Arban has defeated both the mighty Frostborn and the evil of the Seven Swords, and now he only wishes to live quietly with his family. But Ridmark's oldest enemy, the Warden of Urd Morlemoch, has not forgotten him. And the Warden knows a dangerous secret. For the dragons are returning...

The gates between worlds have been thrown open, and armies of invaders have come forth to threaten the realm of Andomhaim. Ridmark Arban is the Shield Knight of Andomhaim, and he and all his allies stand in the invaders' path. But it will take more than swords & magic to win the victory. For Ridmark's foes are led by the Heralds of Ruin, and behind the Heralds is the dark power of the Warden of Urd Morlemoch...

Ridmark Arban is the Shield Knight of Andomhaim, and he has always gone into battle alongside the deadly Third of Nightmane Forest. But now Third finds herself trapped in a strange new world of deadly magic. Unless Third learns to master the dangers of this new world, they will destroy her. Or the Heralds of Ruin will find her and kill her...