Age of Iron (Iron Age, 1)

LEGENDS AREN'T BORN. THEY'RE MADE.
Dug Sealskinner is a down-on-his-luck mercenary traveling south to join up with King Zadar's army. But he keeps rescuing the wrong people.
First Spring, a child he finds scavenging on the battlefield, and then Lowa, one of Zadar's most fearsome warriors, who has vowed revenge on the king for her sister's execution.
Now Dug's on the wrong side of the thousands-strong army he hoped to join ­-- and worse, Zadar has bloodthirsty druid magic on his side. All Dug has is his war hammer, one small child, and one unpredictable, highly-trained warrior with a lust for revenge that might get them all killed . . .