The Last Druid.

A ruthless Roman emperor discovers a secluded Druid stronghold in the mountains of Caledonia, the last remnant of the mystical tribe. When the imperial legions threaten to annihilate the ancient civilization, a peaceful Celtic elder is forced to betray his vow of pacifism and to take up arms to defend his family from the inexorable advance of the Empire in a clash that will decide the fate of an entire culture.