Walking the Shadows

So, you're at school and things aren't great and every night you have these intense dreams, climbing a cliff to find a strange door. Moment you go through the door it is gone and you are in the army. The Roman Army. The one that was massacred two thousand years ago. You find some cool friends, everybody else is trying to kill you. Including a ginger bodybuilder from your own time who wants to change history.
And you cannot wake up.
We all dream, but some dreams are different. Some can steer their dreams to visit the past, look at Cleopatra or attend the games at the Colosseum. Its harmless, they go, they look, they go back to their own time. But a dream traveller has found a way to go back in time and change history, and history has sent a schoolboy to stop him, for no-one can predict what will happen if you change history.
Sammy's dream lands him in a savage land, with mortal danger around every turn. Can he save the course of history before being killed?
This story is set around the events of the Battle of Teutoburg Forest, but it is not about that battle. Very little is known about it, for it happened in a primitive part of the word and those who would normally write these things down were generally killed during the battle. It also happened very long ago, 9AD, so if Jesus was born in the year 0, as in the year between BC and AD, he would have been 8 or 9 years old. That long ago.