Forged In Blood. Rise of the Giants, #4

The brave warriors of Hammer's band of Godless Clan must forge their own path after separating from their families and the only life they've ever known. The world of dangers doesn't forgive the slightest error and Hammer must overcome countless obstacles just to keep himself and his comrades alive. Hammer and his people return to the valley and get the idea to domesticate the Ashtaws the way Mora suggested.
The project could take years and might even cost the men their lives, but this could be the secret to finally defeating the deadly enemies circling and trying to destroy the band. Hammer must learn on the fly how to be the leader his people need him to be. He'll face challenges from the dangerous world around him and from internal conflicts and betrayals within his own band. Everything depends on him-including whether he and his people live or die.