War of the Thunderers

In the time before Camelot, before Arthur, before the sword in the stone
Rome falls!
The servants of chaos seek to dominate what order once ruled. Barbarians invade from all sides. Britannia stand on the brink of collapse.
Only one Roman Legion remains to keep the carnage at bay, the Thunderers. A ragtag group of warriors made up of men of Britannia, Roman soldiers, and a tribe of giant men from a land far to the north battle each threat with finality and victory increasing their renown. As long as the Thunderers remain strong, Britannia cannot fall.
Bevin, a young Britain seeking to blaze his own trail separate from his father, finds himself conscripted as soldier of the Thunderers after proving himself against insurmountable odds. His hopes of glory are dashed due to betrayal. No more, the Thunderers of Britannia are separated on two paths, of darkness and light.
An evil has arisen in the East. The Old Man of the Mountain plans to send an army of Assassins to rule the world. The only hope for humanity is the Thunderers. Their guide is the would-be cesar, Igor Vadim of Arkaim who has evil intent for the Roman Legion in his own bid for conquest.
In the midst of this conflict is small village named Paz who refused to bow to any save their God. The Thunders bound by duty and honor march toward their destiny which means the destruction of Paz. Bevin and a handful of others find that path to be evil.
Can Love and Honor trump duty? Will Darkness reign across the land? Who can survive the War of the Thunderers?