The Shining Company by Rosemary Sutcliff

They attack the group in jest, but Prosper ends up in a fight with a panicked Faelinn, the shieldbearer to Peredur of Rheged. On the third night, Prosper’s party returns, finding the other group asleep. They discover another party completing the same assignment, which leaves a token in their camp as a challenge. So they set out for the Roman fort of Castellum, where they gossip and practice stone-masonry. Prosper and two other shieldbearers are assigned to spend three days doing anything except for sleeping. Conn has no place or role until Prosper sends him on an errand to the weaponsmith and, seeing his fascination with the craft, proposes to grant him an apprenticeship, which would force his father to free him. The Company begins training with its shieldbearers. Prosper meets Cynan Mac Clydno and his devoted friend the Princess Niamh. The feast and sword giving take place, comprising three hundred sons of chieftains from kingdoms across the land (called the Company). Mynyddog’s friend Phanes of Syracuse talks to Prosper, explaining that the King is too ill to participate so his illegitimate son, Ceredig the Fosterling, will take his place in the host.

They expect the host to be primarily a discussion of impending war against the Saxons of Bernicia, who are growing in power. The group arrives at Dyn Eidin to meet with Mynyddog. When Prosper turns sixteen, Gorthyn appoints him his second shield-bearer at the host of Mynyddog the Golden, King of the Gododdin.

This action makes Prosper give his allegiance to the Prince. Prosper, Conn, and Luned plan to kill the hart humanely if the hart is cornered, but Prince Gorthyn calls off the hunt at the sight of it. However, the news reaches the King's son Gorthyn, who arrives intending to hunt the hart. They make a promise to each other to tell no one about it. Prosper, Conn, and Luned see a white hart while searching for their lost dog.

The Shining Company by Rosemary Sutcliff