Let's start at the ending, so that I can say I liked almost everything about this movie... except the ending.
I wasn't dismayed by the fact that there were no CGI or 3-D or other extra-special effects. I am of the generation for whom British novelist Rosemary Sutcliffe's book The Eagle of the Ninth (published 1954) was required reading in elementary school. So, just as it is it is a much-better representation of that story than would have been available before now.
The Eagle of the Ninth is a childrens book, and the first of a fiction series that depicts the Roman occupation of Britain in the second century AD. The movie, The Eagle, is rated PG and intended as family entertainment with just enough blood and gore to amuse 12-year-old boys in these early years of the 21st century. (To wit, the meal of a raw dead rat; one obvious decapitation resulting is a rolling head; several bloody battles and two off-screen throat-slittings.)
For the most part, the film was true to the original work. There were a reasonable number of Celts, Druids, and Picts portrayed battling a beleaguered, smaller number of Roman military and Romans-turned-Caledonians, rather than hordes of any of these races. No gratuitous love story or female characters were added, and in that it was faithful to history as well. There were few if any Roman ladies present in northern England and men posted there generally took local "wives" to bed and fathered mixed-race children who were abandoned when their dads were recalled to Rome.
Pictavia, as the Romans called the land occupied by a tribe they named Picts, is said to have merged with another northern tribe to form the Kingdom of Alba, which we now call Scotland. The Picts never called themselves such; Rome gave names to the people and places they conquered. We don't know what the Picts called themselves but in the movie, they are referred to as the Seal People.
The "seal people" are a reference to an ancient folkloric tale about shape-shifting inhabitants of the Orkney Islands who were said to be able to change their shape from that of a seal to human, so as to mate with human females. These "silkies" or "selkies" were the inspiration for the far-northern inhabitants wearing seal furs and coated in bluish mud that the movie portrays as having devastated the ninth Roman legion.
There were a few token ginger-haired Picts and Caledonians, but if you were looking for a lot of red-haired wives and bairns you would be mistaken, as the red hair for which the Scots and Irish are famous was the result of the Viking blood introduced violently into their cultures some time later.
Most of the action scenes appear to have been shot in Hungary, while the panoramic scenes Esca and Marcus view after they travel past Hadrian's Wall were shot in Scotland. Unfortunately the time of the year portrayed appears to be early spring, as there was still snow on the ground in places and the rain was incessant. So if you are hoping to see green and purple Scottish Highland vistas in the film, you will be disappointed. The film does the Scottish tourism folks no favours.
As was Sutcliffe's intent, screenwriter Jeremy Block's words deliver a message: Rome is bad, freedom is good and Romans are mean, old men who take away the freedom of the poor Britons. At one point, Roman Marcus is reduced to the position of slave, while Esca becomes his supposed master and all manner of behaviour and acts are inflicted upon Marcus with the end result that the young Roman comes to appreciate the plight of Esca and all Roman slaves everywhere.
All in all, I have two major criticisms of this movie.
First, I was expecting British accents for the Roman characters. Maybe I am just conditioned to expect Brit voices when it comes to Romans, having watched and loved all 22 episodes of the BBC television series, Rome. But I just couldn't get past the American and Canadian accents (nod to Donald Sutherland) whenever the "Romans" spoke.
As for the ending... blah. Marcus the Roman and Esca the Briton walk off into the sunset as equals, after Marcus delivers a snipe to a snot-nosed Roman in a toga about his former slave's better understanding of freedom and honour. I pictured Luke Skywalker and Hans Solo. It was lame. And it set up the audience for a sequel that will never be filmed.
Despite its many good qualities, this movie will never make enough at the box office to justify the expense of shooting the next book in Sutcliffe's series. But as for depicting a realistic picture of ancient Scotland, it didn't do badly at all.